J3.x:Developing an MVC Component/Adding Access

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Joomla!

3.x

Tutorial

Developing an MVC Component

This is a multiple-article series of tutorials on how to develop a Model-View-Controller Component for Joomla! Version.

Begin with the Introduction, and navigate the articles in this series by using the navigation button at the bottom or the box to the right (the Articles in this series).

This tutorial is part of the Developing an MVC Component for Joomla! 3.2 tutorial. You are encouraged to read the previous parts of the tutorial before reading this.

In this step we add access capability to our component, which allows us to restrict the set of users who can view our helloworld data. This step really fits before Adding ACL, but is added belatedly for completeness here.

There is a video accompanying this step (which was originally produced at the same time as the other videos for ACL) available at Access Levels.

Introduction

If you're not familiar with Access within Joomla, then it's worthwhile playing around with the functionality – setting access on menuitems and articles, setting the accesslevels of user groups (and hence of users), and confirming that users can see only the items to which they have been granted access. This works on both the site front end, and the admin back end. The diagram shows how Joomla user access levels work.

Each item – eg an article, a menuitem, or in our case a helloworld record – has an access level assigned.

Each user is assigned one or more user groups, and user groups have a hierarchical (tree) structure, so that if a user belongs to a user group which is a child of another, then that user is also a member of the parent user group. Each access level has one more associated user groups, who will then have view access to items which have that access level.

When the user requests to view a particular item, then the functionality

obtains the set of accesslevels that the user has
checks if the accesslevel of the requested item is within the set of accesslevels of that user
if it is, then the item is presented to the user
if it isn't, then an HTTP response with status 403 (forbidden) is returned.

Approach

Database Changes

To enable us to have an Access Level against a helloworld record, we need to specify a new field in the database, which we'll call "access". We'll set the database default value of this access field to be 0, however in the JTable constructor there is code which looks for a database field called "access" and if it finds it then it sets the default value of the access property in the JTable object to have the value specified in the global config (in configuration.php). So we use this mechanism to align with what an administrator would want to have as the default access across the Joomla website.

However, for those helloworld records already present in the database, we don't want to have the access field set to 0 (the SQL default), so after altering the table to introduce the new access field we must update those records. Ideally we should use an install script and perform a SQL UPDATE to set access to JFactory::getConfig()->get('access'), but for simplicity we just use a SQL UPDATE statement to set it to 1 (ie public access).

We also have a change to our content_types field mapping, as described below.

Admin back end changes

To enable the administrator to set this field, we will add an Access field within the back-end edit form, and we use the "accesslevel" field type within the Joomla standard form field types. As is often the case, this field will get automatically saved to the "access" field in the database by our existing code.

On our administrator helloworlds view we'll add a column to display the Access Level assigned to that item. As this should be displayed as a string rather than the int value in the helloworld record, we have to do a SQL JOIN find the associated title of the access level from where they're stored in the viewlevels record.

We will make this column sortable, so we must include options for it in the filter fields xml file and in the helloworlds model.

We also want to restrict the administrator to only those helloworld records that he/she has access to view, so this will involve a filter within the SQL query in our model.

The key Joomla method which we use to find the accesslevels which a user has is JUser::getAuthorisedViewLevels(), and for a user to be allowed to view an item, the item's accesslevel must be within the array of accesslevels returned by getAuthorisedViewLevels(). This is true for both front end and back end.

We will also follow the pattern in Joomla, which specifies that to view an item the user must have access to both the item itself and to the category (if any) associated with the item. Joomla already allows us to set an accesslevel against a category, and where categories are being displayed (both on front end and back end) it filters them to show only those which the user is entitled to see. However, we must write the code in the case where we're displaying helloworld records, to check that the user is entitled to view the associated category as well.

Frontend changes

On the front end we have pages where we display a single helloworld record (our Hello World menuitem) and others where we display a list of records (Category view, our Ajax response to the Search here on the map, and functionality developed in Adding Levels to output a list of children of a helloworld record). What if the visitor to the site doesn't have access to view a record? In this case we could return an error 403 (forbidden) for a single record, and avoid including an inaccessible record in a list.

However, the user may actually have access to the record and the problem is that he/she just hasn't logged in yet. So we'll make it a bit more sophisticated, and check if the user is currently logged in, and adopt the following approach (which reflects the various strategies you might consider for an actual component):

If the user is logged in then

for the Hello World menuitem, if the user doesn't have access then we'll provide an HTTP status 403 (forbidden) and an error message.
for the Category list and Ajax list, if a record can't be accessed then we'll omit it from the list.
for the list of children, we'll just output all the records anyway.

If the user isn't logged in then

for the Hello World menuitem, if the user doesn't have access then we'll provide a notice and a redirect to the login form.
for the Category list, if a record can't be accessed we'll still include it in the list, but add a message to the record prompting the user to login.
for the Ajax list we'll just display the record's link as normal – when the user clicks on it then the action above for the Hello World menuitem will be taken.
for the list of children, we'll just output all the records anyway.

To find if the user is logged in we use JFactory::getUser()->get('guest') which returns 1 if just a guest on the site, ie not logged in, and returns 0 if the user is logged in.

The split of functionality we'll adopt is:

Hello World menuitem:

Model: determine if the user has access to the record
View: if the user doesn't have access then display an error (with a redirect to login) or a notice (with a redirect to login) depending upon whether the user is logged in or not.

Category list:

Model: we'll post-process the items returned from the query, and for those where the user doesn't have access we'll remove them if the user is logged in, or set a "no-access" flag if the user isn't logged in
Layout: we'll display the record differently if the no-access flag is set

Ajax list:

If the user is logged in, then we'll change the SQL query to omit records the user doesn't have access to, but continue to return all the records if the user isn't logged in.

List of children:

no change - all the records will be returned regardless of whether the user has access or not.

Finally, as helloworld records may be viewed (to a certain extent) via the tags functionality, we update our field mappings so that our access field is copied into the ucm_content table core_access field. This means that the same restrictions will apply to viewing both the helloworld record and its copy in the ucm_content table.

(If we didn't copy the field into ucm_content then Joomla's tag functionality would store the default of 0 in its core_access field. The JTable constructor doesn't set the global config access value here because the ucm_content field is called "core_access" rather than "access". Whenever Joomla's com_tags component displays the records having a particular tag, it always includes records with a core_access of 0, and hence would show helloworld records which the user couldn't access, so that when the user clicked on them then the user would receive the "no access" notification).

In the previous step we needed to set a published field in the front end form to get the default value of 1 carried through to the ucm_content table. However, we don't need to do the same for the access field, because of the way the JTable constructor sets the default value into the JTable object.

Database

We add our new access field to the helloworld record, and include this in the set of fields which are mapped to the ucm_content copy.

admin/sql/updates/mysql/0.0.29.sql

ALTER TABLE `#__helloworld` ADD COLUMN `access` tinyint(4) NOT NULL DEFAULT '0' AFTER `published`;
UPDATE `#__helloworld` SET `access` = 1; 

UPDATE `#__content_types` SET
`field_mappings` = 
'{"common": {
	"core_content_item_id": "id",
	"core_title": "greeting",
	"core_state": "published",
	"core_alias": "alias",
	"core_language":"language", 
	"core_created_time": "created",
	"core_body": "description",
	"core_access": "access",
	"core_catid": "catid"
  }}'
WHERE `type_alias` = 'com_helloworld.helloworld';

admin/sql/install.mysql.utf8.sql

DROP TABLE IF EXISTS `#__helloworld`;

CREATE TABLE `#__helloworld` (
	`id`       INT(11)     NOT NULL AUTO_INCREMENT,
	`asset_id` INT(10)     NOT NULL DEFAULT '0',
	`created`  DATETIME    NOT NULL DEFAULT '0000-00-00 00:00:00',
	`created_by`  INT(10) UNSIGNED NOT NULL DEFAULT '0',
	`checked_out` INT(10) NOT NULL DEFAULT '0',
	`checked_out_time` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00',
	`greeting` VARCHAR(25) NOT NULL,
	`description` VARCHAR(4000) NOT NULL DEFAULT '',
	`alias`  VARCHAR(40)  NOT NULL DEFAULT '',
	`language`  CHAR(7)  NOT NULL DEFAULT '*',
	`parent_id`	int(10)    NOT NULL DEFAULT '1',
	`level`	int(10)    NOT NULL DEFAULT '0',
	`path`	VARCHAR(400)    NOT NULL DEFAULT '',
	`lft`	int(11)    NOT NULL DEFAULT '0',
	`rgt`	int(11)    NOT NULL DEFAULT '0',
	`published` tinyint(4) NOT NULL DEFAULT '1',
	`access` tinyint(4) NOT NULL DEFAULT '0',
	`catid`	    int(11)    NOT NULL DEFAULT '0',
	`params`   VARCHAR(1024) NOT NULL DEFAULT '',
	`image`   VARCHAR(1024) NOT NULL DEFAULT '',
	`latitude` DECIMAL(9,7) NOT NULL DEFAULT 0.0,
	`longitude` DECIMAL(10,7) NOT NULL DEFAULT 0.0,
	PRIMARY KEY (`id`)
)
	ENGINE =MyISAM
	AUTO_INCREMENT =0
	DEFAULT CHARSET =utf8;

CREATE UNIQUE INDEX `aliasindex` ON `#__helloworld` (`alias`, `catid`);

INSERT INTO `#__helloworld` (`greeting`,`alias`,`language`, `parent_id`, `level`, `path`, `lft`, `rgt`, `published`) VALUES
('helloworld root','helloworld-root-alias','en-GB', 0, 0, '', 0, 5, 1),
('Hello World!','hello-world','en-GB', 1, 1, 'hello-world', 1, 2, 0),
('Goodbye World!','goodbye-world','en-GB', 1, 1, 'goodbye-world', 3, 4, 0);

INSERT INTO `#__content_types` (`type_title`, `type_alias`, `content_history_options`, `table`, `field_mappings`, `router`) 
VALUES
('Helloworld', 'com_helloworld.helloworld', 
'{"formFile":"administrator\\/components\\/com_helloworld\\/models\\/forms\\/helloworld.xml", 
"hideFields":["asset_id","checked_out","checked_out_time","version","lft","rgt","level","path"], 
"ignoreChanges":["checked_out", "checked_out_time", "path"],
"convertToInt":[], 
"displayLookup":[
{"sourceColumn":"created_by","targetTable":"#__users","targetColumn":"id","displayColumn":"name"},
{"sourceColumn":"parent_id","targetTable":"#__helloworld","targetColumn":"id","displayColumn":"greeting"},
{"sourceColumn":"catid","targetTable":"#__categories","targetColumn":"id","displayColumn":"title"}]}',
'{"special":{"dbtable":"#__helloworld","key":"id","type":"Helloworld","prefix":"HelloworldTable","config":"array()"},
"common":{"dbtable":"#__ucm_content","key":"ucm_id","type":"Corecontent","prefix":"JTable","config":"array()"}}',
'{"common": {
	"core_content_item_id": "id",
	"core_title": "greeting",
	"core_state": "published",
	"core_alias": "alias",
	"core_language":"language", 
	"core_created_time": "created",
	"core_body": "description",
	"core_access": "access",
	"core_catid": "catid"
  }}',
'HelloworldHelperRoute::getHelloworldRoute'),
('Helloworld Category', 'com_helloworld.category',
'{"formFile":"administrator\\/components\\/com_categories\\/models\\/forms\\/category.xml", 
"hideFields":["asset_id","checked_out","checked_out_time","version","lft","rgt","level","path","extension"], 
"ignoreChanges":["modified_user_id", "modified_time", "checked_out", "checked_out_time", "version", "hits", "path"],
"convertToInt":["publish_up", "publish_down"], 
"displayLookup":[
{"sourceColumn":"created_user_id","targetTable":"#__users","targetColumn":"id","displayColumn":"name"},
{"sourceColumn":"access","targetTable":"#__viewlevels","targetColumn":"id","displayColumn":"title"},
{"sourceColumn":"modified_user_id","targetTable":"#__users","targetColumn":"id","displayColumn":"name"},
{"sourceColumn":"parent_id","targetTable":"#__categories","targetColumn":"id","displayColumn":"title"}]}',
'{"special":{"dbtable":"#__categories","key":"id","type":"Category","prefix":"JTable","config":"array()"},
"common":{"dbtable":"#__ucm_content","key":"ucm_id","type":"Corecontent","prefix":"JTable","config":"array()"}}',
'{"common": {
	"core_content_item_id":"id",
	"core_title":"title",
	"core_state":"published",
	"core_alias":"alias",
	"core_created_time":"created_time",
	"core_modified_time":"modified_time",
	"core_body":"description", 
	"core_hits":"hits",
	"core_publish_up":"null",
	"core_publish_down":"null",
	"core_access":"access", 
	"core_params":"params", 
	"core_featured":"null", 
	"core_metadata":"metadata", 
	"core_language":"language", 
	"core_images":"null", 
	"core_urls":"null", 
	"core_version":"version",
	"core_ordering":"null", 
	"core_metakey":"metakey", 
	"core_metadesc":"metadesc", 
	"core_catid":"parent_id", 
	"core_xreference":"null", 
	"asset_id":"asset_id"}, 
  "special":{
    "parent_id":"parent_id",
	"lft":"lft",
	"rgt":"rgt",
	"level":"level",
	"path":"path",
	"extension":"extension",
	"note":"note"}}',
'HelloworldHelperRoute::getCategoryRoute');

Admin Edit Form

We add the access field into the form xml definition. That's all we need to do to enable the administrator to view and set that field, and to get it written to the database.

admin/models/forms/helloworld.xml

<?xml version="1.0" encoding="utf-8"?>
<form
				addrulepath="/administrator/components/com_helloworld/models/rules"
>
	<fieldset
				name="details"
				label="COM_HELLOWORLD_HELLOWORLD_DETAILS"
	>
		<field
				name="id"
				type="hidden"
				/>
		<field
				name="greeting"
				type="text"
				label="COM_HELLOWORLD_HELLOWORLD_GREETING_LABEL"
				description="COM_HELLOWORLD_HELLOWORLD_GREETING_DESC"
				size="40"
				class="inputbox validate-greeting"
				validate="greeting"
				required="true"
				default=""
				/>
		<field 
				name="alias" 
				type="text" 
				label="JFIELD_ALIAS_LABEL"
				description="JFIELD_ALIAS_DESC"
				hint="JFIELD_ALIAS_PLACEHOLDER"
				size="40" 
				/>
		<field
				name="catid"
				type="category"
				extension="com_helloworld"
				class="inputbox"
				default=""
				label="COM_HELLOWORLD_HELLOWORLD_FIELD_CATID_LABEL"
				description="COM_HELLOWORLD_HELLOWORLD_FIELD_CATID_DESC"
				required="true"
		>
			<option value="0">JOPTION_SELECT_CATEGORY</option>
		</field>
		<field
				name="latitude"
				type="number"
				label="COM_HELLOWORLD_HELLOWORLD_FIELD_LATITUDE_LABEL"
				description="COM_HELLOWORLD_HELLOWORLD_FIELD_LATITUDE_DESC"
				min="-90.0"
				max="90.0"
				class="inputbox"
				required="true"
				default="0.0"
				/>
		<field
				name="longitude"
				type="number"
				label="COM_HELLOWORLD_HELLOWORLD_FIELD_LONGITUDE_LABEL"
				description="COM_HELLOWORLD_HELLOWORLD_FIELD_LONGITUDE_DESC"
				min="-180.0"
				max="180.0"
				class="inputbox"
				required="true"
				default="0.0"
				/>
		<field  
                name="language" 
        		type="contentlanguage" 
                label="JFIELD_LANGUAGE_LABEL"
				description="COM_HELLOWORLD_HELLOWORLD_FIELD_LANGUAGE_DESC"
		>
			<option value="*">JALL</option>
		</field>
		<field 	name="published" 
				type="list" 
				label="JSTATUS"
				description="JFIELD_PUBLISHED_DESC" 
				class="chzn-color-state"
				filter="intval" 	
				size="1" 
				default="1"
		>
			<option value="1">
				JPUBLISHED</option>
			<option value="0">
				JUNPUBLISHED</option>
		</field>
		<field 
				name="tags" 
				type="tag"
				label="JTAG" 
				description="JTAG_DESC"
				multiple="true"
		>
		</field>
		<field  
				name="access" 
				type="accesslevel" 
				label="JFIELD_ACCESS_LABEL"
				description="JFIELD_ACCESS_DESC"
		>
		</field>
		<field
				name="parent_id"
				type="helloworldparent"
				label="COM_HELLOWORLD_HELLOWORLD_FIELD_PARENT_LABEL"
				description="COM_HELLOWORLD_HELLOWORLD_FIELD_PARENT_DESC"
				default="1"
				filter="int">
		</field>
		<field
				name="helloworldordering"
				type="helloworldordering"
				label="JFIELD_ORDERING_LABEL"
				description="JFIELD_ORDERING_DESC"
				filter="int"
				size="1">
		</field>
		<field 	name="version_note"
				type="text"
				label="JGLOBAL_FIELD_VERSION_NOTE_LABEL"
				description="JGLOBAL_FIELD_VERSION_NOTE_DESC"
				class="inputbox" 
				size="45"
				labelclass="control-label">
		</field>
    </fieldset>
		<field 	name="description" 
				type="editor"
				label="COM_HELLOWORLD_HELLOWORLD_FIELD_DESCRIPTION_LABEL" 
				description="COM_HELLOWORLD_HELLOWORLD_FIELD_DESCRIPTION_DESC"
				filter="JComponentHelper::filterText" 
				buttons="true" 
		/>
	<fields name="imageinfo">
		<fieldset
				name="image-info"
				label="COM_HELLOWORLD_IMAGE_FIELDS"
		>
			<field
                name="image"
                type="media"
                preview="tooltip"
                label="COM_HELLOWORLD_HELLOWORLD_FIELD_IMAGE_LABEL"
                description="COM_HELLOWORLD_HELLOWORLD_FIELD_IMAGE_DESC" />
            <field name="alt"
                type="text"
                label="COM_HELLOWORLD_HELLOWORLD_FIELD_ALT_LABEL"
                description="COM_HELLOWORLD_HELLOWORLD_FIELD_ALT_DESC"
                size="30"/>
            <field name="caption"
                type="text"
                label="COM_HELLOWORLD_HELLOWORLD_FIELD_CAPTION_LABEL"
                description="COM_HELLOWORLD_HELLOWORLD_FIELD_CAPTION_DESC"
                size="30"/>
		</fieldset>
	</fields>
	<fields name="params">
		<fieldset
				name="params"
				label="JGLOBAL_FIELDSET_DISPLAY_OPTIONS"
		>
			<field
					name="show_category"
					type="list"
					label="COM_HELLOWORLD_HELLOWORLD_FIELD_SHOW_CATEGORY_LABEL"
					description="COM_HELLOWORLD_HELLOWORLD_FIELD_SHOW_CATEGORY_DESC"
					default=""
			>
				<option value="">JGLOBAL_USE_GLOBAL</option>
				<option value="0">JHIDE</option>
				<option value="1">JSHOW</option>
			</field>
		</fieldset>
	</fields>
	<fieldset
			name="accesscontrol"
			label="COM_HELLOWORLD_FIELDSET_RULES"
	>
    	<field
				name="asset_id"
				type="hidden"
				filter="unset"
				/>
    	<field
				name="rules"
				type="rules"
				label="COM_HELLOWORLD_FIELD_RULES_LABEL"
				filter="rules"
				validate="rules"
				class="inputbox"
				component="com_helloworld"
				section="message"
				/>
    </fieldset>
</form>

Admin Helloworlds Display

Updates to 3 files are required to implement the necessary changes:

the layout file
the filter fields xml definition
the helloworlds model

In the layout file we replace the 4 columns associated with the nested table structure (lft, rgt, level, parent) with the access column, and make it a sortable column.

admin/views/helloworlds/tmpl/default.php

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */

// No direct access to this file
defined('_JEXEC') or die('Restricted Access');

use Joomla\Registry\Registry;

JHtml::_('formbehavior.chosen', 'select');

$listOrder     = $this->escape($this->state->get('list.ordering'));
$listDirn      = $this->escape($this->state->get('list.direction'));
$user = JFactory::getUser();
$userId = $user->get('id');
$saveOrder = ($listOrder == 'lft' && strtolower($listDirn) == 'asc');
if ($saveOrder)
{
        $saveOrderingUrl = 'index.php?option=com_helloworld&task=helloworlds.saveOrderAjax&tmpl=component';
        // pass true as parameter 7 to indicate that we have a nested set
        JHtml::_('sortablelist.sortable', 'helloworldList', 'adminForm', strtolower($listDirn), $saveOrderingUrl, false, true);
}
$assoc = JLanguageAssociations::isEnabled();
$authorFieldwidth = $assoc ? "10%" : "25%";
JLoader::register('JHtmlHelloworlds', JPATH_ADMINISTRATOR . '/components/com_helloworld/helpers/html/helloworlds.php');
?>
<form action="index.php?option=com_helloworld&view=helloworlds" method="post" id="adminForm" name="adminForm">
        <div id="j-sidebar-container" class="span2">
                <?php echo JHtmlSidebar::render(); ?>
        </div>
        <div id="j-main-container" class="span10">
        <div class="row-fluid">
            <div class="span6">
                <?php echo JText::_('COM_HELLOWORLD_HELLOWORLDS_FILTER'); ?>
                <?php
                    echo JLayoutHelper::render(
                        'joomla.searchtools.default',
                        array('view' => $this)
                    );
                ?>
            </div>
        </div>
        <table class="table table-striped table-hover" id="helloworldList">
            <thead>
            <tr>
                <th width="1%">
                    <?php echo JHtml::_('searchtools.sort', '', 'lft', $listDirn, $listOrder, null, 'asc', 'JGRID_HEADING_ORDERING', 'icon-menu-2'); ?>
                </th>
                <th width="1%"><?php echo JText::_('COM_HELLOWORLD_NUM'); ?></th>
                <th width="1%">
                    <?php echo JHtml::_('grid.checkall'); ?>
                </th>
                <th width="10%">
                    <?php echo JHtml::_('searchtools.sort', 'COM_HELLOWORLD_HELLOWORLDS_NAME', 'greeting', $listDirn, $listOrder); ?>
                </th>
                <th width="10%">
                    <?php echo JText::_('COM_HELLOWORLD_HELLOWORLDS_POSITION'); ?>
                </th>
                <th width="10%">
                    <?php echo JText::_('COM_HELLOWORLD_HELLOWORLDS_IMAGE'); ?>
                </th>
                <th width="20%">
                    <?php echo JHtml::_('searchtools.sort',  'JGRID_HEADING_ACCESS', 'access', $listDirn, $listOrder); ?>
                </th>
                <?php if ($assoc) : ?>
                    <th width="10%">
                        <?php echo JHtml::_('searchtools.sort', 'COM_HELLOWORLD_HELLOWORLDS_ASSOCIATIONS', 'association', $listDirn, $listOrder); ?>
                    </th>
                <?php endif; ?>
                <th width="<?php echo $authorFieldwidth; ?>">
                    <?php echo JHtml::_('searchtools.sort', 'COM_HELLOWORLD_AUTHOR', 'author', $listDirn, $listOrder); ?>
                </th>
                <th width="10%">
                    <?php echo JHtml::_('searchtools.sort', 'COM_HELLOWORLD_LANGUAGE', 'language', $listDirn, $listOrder); ?>
                </th>
                <th width="10%">
                    <?php echo JHtml::_('searchtools.sort', 'COM_HELLOWORLD_CREATED_DATE', 'created', $listDirn, $listOrder); ?>
                </th>
                <th width="5%">
                    <?php echo JHtml::_('searchtools.sort', 'COM_HELLOWORLD_PUBLISHED', 'published', $listDirn, $listOrder); ?>
                </th>
                <th width="2%">
                    <?php echo JHtml::_('searchtools.sort', 'COM_HELLOWORLD_ID', 'id', $listDirn, $listOrder); ?>
                </th>
            </tr>
            </thead>
            <tfoot>
                <tr>
                    <td colspan="5">
                        <?php echo $this->pagination->getListFooter(); ?>
                    </td>
                </tr>
            </tfoot>
            <tbody>
                <?php if (!empty($this->items)) : ?>
                    <?php foreach ($this->items as $i => $row) :
                        $link = JRoute::_('index.php?option=com_helloworld&task=helloworld.edit&id=' . $row->id);
                        $row->image = new Registry;
                        $row->image->loadString($row->imageInfo);
                        // create a list of the parents up the hierarchy to the root 
                        if ($row->level > 1)
                        {
                            $parentsStr = '';
                            $_currentParentId = $row->parent_id;
                            $parentsStr = ' ' . $_currentParentId;
                            for ($j = 0; $j < $row->level; $j++)
                            {
                                foreach ($this->ordering as $k => $v)
                                {
                                    $v = implode('-', $v);
                                    $v = '-' . $v . '-';
                                    if (strpos($v, '-' . $_currentParentId . '-') !== false)
                                    {
                                        $parentsStr .= ' ' . $k;
                                        $_currentParentId = $k;
                                        break;
                                    }
                                }
                            }
                        }
                        else
                        {
                            $parentsStr = '';
                        }
                    ?>
                        <tr class="row<?php echo $i % 2; ?>" sortable-group-id="<?php echo $row->parent_id; ?>" item-id="<?php echo $row->id; ?>" parents="<?php echo $parentsStr; ?>" level="<?php echo $row->level; ?>">
                            <td><?php
                                $iconClass = '';
                                $canReorder  = $user->authorise('core.edit.state', 'com_helloworld.helloworld.' . $row->id);
                                if (!$canReorder)
                                {
                                    $iconClass = ' inactive';
                                }
                                elseif (!$saveOrder)
                                {
                                    $iconClass = ' inactive tip-top hasTooltip" title="' . JHtml::_('tooltipText', 'JORDERINGDISABLED');
                                }
                                ?>
                                <span class="sortable-handler<?php echo $iconClass ?>">
                                    <span class="icon-menu" aria-hidden="true"></span>
                                </span>
                                <?php if ($canReorder && $saveOrder) : ?>
                                    <input type="text" style="display:none" name="order[]" size="5" value="<?php echo $row->lft; ?>" class="width-20 text-area-order" />
                                <?php endif; ?>
                            </td>
                            <td><?php echo $this->pagination->getRowOffset($i); ?></td>
                            <td>
                                <?php echo JHtml::_('grid.id', $i, $row->id); ?>
                            </td>
                            <td>
                                <?php $prefix = JLayoutHelper::render('joomla.html.treeprefix', array('level' => $row->level)); ?>
                                <?php echo $prefix; ?>
                                <?php if ($row->checked_out) : ?>
                                    <?php $canCheckin = $user->authorise('core.manage', 'com_checkin') || $row->checked_out == $userId; ?>
                                    <?php echo JHtml::_('jgrid.checkedout', $i, $row->editor, $row->checked_out_time, 'helloworlds.', $canCheckin); ?>
                                <?php endif; ?>
                                <a href="<?php echo $link; ?>" title="<?php echo JText::_('COM_HELLOWORLD_EDIT_HELLOWORLD'); ?>">
                                    <?php echo $row->greeting; ?>
                                </a>
                                <span class="small break-word">
                                        <?php echo JText::sprintf('JGLOBAL_LIST_ALIAS', $this->escape($row->alias)); ?>
                                </span>
                                <div class="small">
                                    <?php echo JText::_('JCATEGORY') . ': ' . $this->escape($row->category_title); ?>
                                </div>
                                <div class="small">
                                    <?php echo 'Path: ' . $this->escape($row->path); ?>
                                </div>
                            </td>
                            <td align="center">
                                <?php echo "[" . $row->latitude . ", " . $row->longitude . "]"; ?>
                            </td>
                            <td align="center">
                                <?php
                                    $caption = $row->image->get('caption') ? : '' ;
                                    $src = JURI::root() . ($row->image->get('image') ? : '' );
                                    $html = '<p class="hasTooltip" style="display: inline-block" data-html="true" data-toggle="tooltip" data-placement="right" title="<img width=\'100px\' height=\'100px\' src=\'%s\'>">%s</p>';
                                    echo sprintf($html, $src, $caption);  ?>
                            </td>
                            <td align="center">
                                <?php echo $this->escape($row->access_level); ?>
                            </td>
                            <?php if ($assoc) : ?>
                                <td align="center">
                                    <?php if ($row->association) : ?>
                                        <?php echo JHtml::_('helloworlds.association', $row->id); ?>
                                    <?php endif; ?>
                                </td>
                            <?php endif; ?>
                            <td align="center">
                                <?php echo $row->author; ?>
                            </td>
                            <td align="center">
                                <?php echo JLayoutHelper::render('joomla.content.language', $row); ?>
                            </td>
                            <td align="center">
                                <?php echo substr($row->created, 0, 10); ?>
                            </td>
                            <td align="center">
                                <?php echo JHtml::_('jgrid.published', $row->published, $i, 'helloworlds.', true, 'cb'); ?>
                            </td>
                            <td align="center">
                                <?php echo $row->id; ?>
                            </td>
                        </tr>
                    <?php endforeach; ?>
                <?php endif; ?>
            </tbody>
        </table>
        <input type="hidden" name="task" value=""/>
        <input type="hidden" name="boxchecked" value="0"/>
        <?php echo JHtml::_('form.token'); ?>
    </div>
</form>

Secondly, in the filter helloworlds form definition we add the 2 options for sorting by the access column.

admin/models/forms/filter_helloworlds.xml

<?xml version="1.0" encoding="utf-8"?>
<form>
	<fields name="filter">
		<field
			name="search"
			type="text"
			label="COM_BANNERS_SEARCH_IN_TITLE"
			hint="JSEARCH_FILTER"
			class="js-stools-search-string"
		/>
		<field
			name="published"
			type="status"
			label="JOPTION_SELECT_PUBLISHED"
			description="JOPTION_SELECT_PUBLISHED_DESC"
			onchange="this.form.submit();"
			>
			<option value="">JOPTION_SELECT_PUBLISHED</option>
		</field>
		<field
			name="language"
			type="contentlanguage"
			label="JOPTION_FILTER_LANGUAGE"
			description="JOPTION_FILTER_LANGUAGE_DESC"
			onchange="this.form.submit();"
			>
			<option value="">JOPTION_SELECT_LANGUAGE</option>
			<option value="*">JALL</option>
		</field>
		<field
			name="category_id"
			type="category"
			label="JOPTION_FILTER_CATEGORY"
			extension="com_helloworld"
			onchange="this.form.submit();"
			published="0,1,2"
			>
			<option value="">JOPTION_SELECT_CATEGORY</option>
		</field>
	</fields>
	<fields name="list">
		<field
			name="fullordering"
			type="list"
			label="COM_HELLOWORLD_LIST_FULL_ORDERING"
			description="COM_HELLOWORLD_LIST_FULL_ORDERING_DESC"
			onchange="this.form.submit();"
			default="greeting ASC"
			>
			<option value="">JGLOBAL_SORT_BY</option>
			<option value="ordering ASC">COM_HELLOWORLD_ORDERING_ASC</option>
			<option value="ordering DESC">COM_HELLOWORLD_ORDERING_DESC</option>
			<option value="greeting ASC">COM_HELLOWORLD_GREETING_ASC</option>
			<option value="greeting DESC">COM_HELLOWORLD_GREETING_DESC</option>
			<option value="id ASC">JGRID_HEADING_ID_ASC</option>
			<option value="id DESC">JGRID_HEADING_ID_DESC</option>
			<option value="published ASC">COM_HELLOWORLD_PUBLISHED_ASC</option>
			<option value="published DESC">COM_HELLOWORLD_PUBLISHED_DESC</option>
			<option value="author ASC">COM_HELLOWORLD_AUTHOR_ASC</option>
			<option value="author DESC">COM_HELLOWORLD_AUTHOR_DESC</option>
			<option value="created ASC">COM_HELLOWORLD_CREATED_ASC</option>
			<option value="created DESC">COM_HELLOWORLD_CREATED_DESC</option>
			<option value="language ASC">COM_HELLOWORLD_LANGUAGE_ASC</option>
			<option value="language DESC">COM_HELLOWORLD_LANGUAGE_DESC</option>
			<option value="access ASC">COM_HELLOWORLD_ACCESS_ASC</option>
			<option value="access DESC">COM_HELLOWORLD_ACCESS_DESC</option>
			<option value="association ASC">COM_HELLOWORLD_ASSOCIATION_ASC</option>
			<option value="association DESC">COM_HELLOWORLD_ASSOCIATION_DESC</option>
		</field>
		<field
			name="limit"
			type="limitbox"
			class="input-mini"
			default="25"
			label="COM_CONTENT_LIST_LIMIT"
			description="COM_HELLOWORLD_LIST_LIMIT_DESC"
			onchange="this.form.submit();"
		/>
	</fields>
</form>

Thirdly we must change the helloworlds model

to include the access field in the query, and translate the access value into the name of that access level,
to include the access field within the list of sort fields ($config array),
to restrict the record returned to those which the user has access to see, by adding an additional SQL WHERE clause.

Note that we must check specifically for the user being a Super User ($user->authorise('core.admin') returns true), as they should be able to see everything, regardless of access.

admin/models/helloworlds.php

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */
// No direct access to this file
defined('_JEXEC') or die('Restricted access');

/**
 * HelloWorldList Model
 *
 * @since  0.0.1
 */
class HelloWorldModelHelloWorlds extends JModelList
{
        /**
         * Constructor.
         *
         * @param   array  $config  An optional associative array of configuration settings.
         *
         * @see     JController
         * @since   1.6
         */
        public function __construct($config = array())
        {
                if (empty($config['filter_fields']))
                {
                        $config['filter_fields'] = array(
                                'id',
                                'greeting',
                                'author',
                                'created',
                                'language',
                                'lft',
                                'category_id',
                                'access',
                                'association',
                                'published'
                        );
                }

                parent::__construct($config);
        }

        protected function populateState($ordering = 'lft', $direction = 'asc')
        {
                $app = JFactory::getApplication();

                // Adjust the context to support modal layouts.
                if ($layout = $app->input->get('layout'))
                {
                        $this->context .= '.' . $layout;
                }

                // Adjust the context to support forced languages.
                $forcedLanguage = $app->input->get('forcedLanguage', '', 'CMD');
                if ($forcedLanguage)
                {
                        $this->context .= '.' . $forcedLanguage;
                }

                parent::populateState($ordering, $direction);
        
                // If there's a forced language then define that filter for the query where clause
                if (!empty($forcedLanguage))
                {
                        $this->setState('filter.language', $forcedLanguage);
                }
        }

        /**
         * Method to build an SQL query to load the list data.
         *
         * @return      string  An SQL query
         */
        protected function getListQuery()
        {
                // Initialize variables.
                $db    = JFactory::getDbo();
                $query = $db->getQuery(true);
                $user = JFactory::getUser();

                // Create the base select statement.
                $query->select('a.id as id, a.greeting as greeting, a.published as published, a.created as created, a.access as access,
                          a.checked_out as checked_out, a.checked_out_time as checked_out_time, a.catid as catid,
                          a.lft as lft, a.rgt as rgt, a.parent_id as parent_id, a.level as level, a.path as path,
                          a.image as imageInfo, a.latitude as latitude, a.longitude as longitude, a.alias as alias, a.language as language')
                          ->from($db->quoteName('#__helloworld', 'a'));

                // Join over the categories.
                $query->select($db->quoteName('c.title', 'category_title'))
                        ->join('LEFT', $db->quoteName('#__categories', 'c') . ' ON c.id = a.catid');
        
                // Join with users table to get the username of the author
                $query->select($db->quoteName('u.username', 'author'))
                        ->join('LEFT', $db->quoteName('#__users', 'u') . ' ON u.id = a.created_by');

                // Join with users table to get the username of the person who checked the record out
                $query->select($db->quoteName('u2.username', 'editor'))
                        ->join('LEFT', $db->quoteName('#__users', 'u2') . ' ON u2.id = a.checked_out');

                // Join with languages table to get the language title and image to display
                // Put these into fields called language_title and language_image so that 
                // we can use the little com_content layout to display the map symbol
                $query->select($db->quoteName('l.title', 'language_title') . "," .$db->quoteName('l.image', 'language_image'))
                        ->join('LEFT', $db->quoteName('#__languages', 'l') . ' ON l.lang_code = a.language');

                // Join over the associations - we just want to know if there are any, at this stage
                if (JLanguageAssociations::isEnabled())
                {
                        $query->select('COUNT(asso2.id)>1 as association')
                                ->join('LEFT', '#__associations AS asso ON asso.id = a.id AND asso.context=' . $db->quote('com_helloworld.item'))
                                ->join('LEFT', '#__associations AS asso2 ON asso2.key = asso.key')
                                ->group('a.id');
                }

                // Join over the access levels, to get the name of the access level
                $query->select('v.title AS access_level')
                        ->join('LEFT', '#__viewlevels AS v ON v.id = a.access');

                // Filter: like / search
                $search = $this->getState('filter.search');

                if (!empty($search))
                {
                        $like = $db->quote('%' . $search . '%');
                        $query->where('greeting LIKE ' . $like);
                }

                // Filter by published state
                $published = $this->getState('filter.published');

                if (is_numeric($published))
                {
                        $query->where('a.published = ' . (int) $published);
                }
                elseif ($published === '')
                {
                        $query->where('(a.published IN (0, 1))');
                }

                // Filter by language, if the user has set that in the filter field
                $language = $this->getState('filter.language');
                if ($language)
                {
                        $query->where('a.language = ' . $db->quote($language));
                }

                // Filter by categories
                $catid = $this->getState('filter.category_id');
                if ($catid)
                {
                        $query->where("a.catid = " . $db->quote($db->escape($catid)));
                }

                // Display only records to which the user has access
                if (!$user->authorise('core.admin'))  // ie if not SuperUser
                {
                        $userAccessLevels = implode(',', $user->getAuthorisedViewLevels());
                        $query->where('a.access IN (' . $userAccessLevels . ')');
                        $query->where('c.access IN (' . $userAccessLevels . ')');
                }

                // exclude root helloworld record
                $query->where('a.id > 1');

                // Add the list ordering clause.
                $orderCol       = $this->state->get('list.ordering', 'lft');
                $orderDirn      = $this->state->get('list.direction', 'asc');

                $query->order($db->escape($orderCol) . ' ' . $db->escape($orderDirn));

                return $query;
        }
}

Front End Hello World Menuitem and Ajax Display

In the model for the single record display we set an item property canAccess, depending upon whether the user has access to the record or not. Also we change the SQL query for the Ajax response to exclude those records which a logged-in user can't access.

site/models/helloworld.php

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */

// No direct access to this file
defined('_JEXEC') or die('Restricted access');

JLoader::register('HelloworldHelperRoute', JPATH_ROOT . '/components/com_helloworld/helpers/route.php');

/**
 * HelloWorld Model
 *
 * @since  0.0.1
 */
class HelloWorldModelHelloWorld extends JModelItem
{
	/**
	 * @var object item
	 */
	protected $item;

	/**
	 * Method to auto-populate the model state.
	 *
	 * This method should only be called once per instantiation and is designed
	 * to be called on the first call to the getState() method unless the model
	 * configuration flag to ignore the request is set.
	 *
	 * Note. Calling getState in this method will result in recursion.
	 *
	 * @return	void
	 * @since	2.5
	 */
	protected function populateState()
	{
		// Get the message id
		$jinput = JFactory::getApplication()->input;
		$id     = $jinput->get('id', 1, 'INT');
		$this->setState('message.id', $id);

		// Load the parameters.
		$this->setState('params', JFactory::getApplication()->getParams());
		parent::populateState();
	}

	/**
	 * Method to get a table object, load it if necessary.
	 *
	 * @param   string  $type    The table name. Optional.
	 * @param   string  $prefix  The class prefix. Optional.
	 * @param   array   $config  Configuration array for model. Optional.
	 *
	 * @return  JTable  A JTable object
	 *
	 * @since   1.6
	 */
	public function getTable($type = 'HelloWorld', $prefix = 'HelloWorldTable', $config = array())
	{
		return JTable::getInstance($type, $prefix, $config);
	}

	/**
	 * Get the message
	 * @return object The message to be displayed to the user
	 */
	public function getItem($id = null)
	{
		if (!isset($this->item) || !is_null($id)) 
		{
			$id    = is_null($id) ? $this->getState('message.id') : $id;
			$db    = JFactory::getDbo();
			$query = $db->getQuery(true);
			$query->select('h.greeting, h.params, h.image as image, c.title as category, c.access as catAccess, 
						h.latitude as latitude, h.longitude as longitude, h.access as access,
						h.id as id, h.alias as alias, h.catid as catid, h.parent_id as parent_id, h.level as level, h.description as description')
				  ->from('#__helloworld as h')
				  ->leftJoin('#__categories as c ON h.catid=c.id')
				  ->where('h.id=' . (int)$id);

			if (JLanguageMultilang::isEnabled())
			{
				$lang = JFactory::getLanguage()->getTag();
				$query->where('h.language IN ("*","' . $lang . '")');
			}

			$db->setQuery((string)$query);
		
			if ($this->item = $db->loadObject()) 
			{
				// Load the JSON string
				$params = new JRegistry;
				$params->loadString($this->item->params, 'JSON');
				$this->item->params = $params;

				// Merge global params with item params
				$params = clone $this->getState('params');
				$params->merge($this->item->params);
				$this->item->params = $params;

				// Convert the JSON-encoded image info into an array
				$image = new JRegistry;
				$image->loadString($this->item->image, 'JSON');
				$this->item->imageDetails = $image;

				// Check if the user can access this record (and category)
				$user = JFactory::getUser();
				$userAccessLevels = $user->getAuthorisedViewLevels();
				if ($user->authorise('core.admin')) // ie superuser
				{
					$this->item->canAccess = true;
				}
				else
				{
					if ($this->item->catid == 0)
					{
						$this->item->canAccess = in_array($this->item->access, $userAccessLevels);
					}
					else
					{
						$this->item->canAccess = in_array($this->item->access, $userAccessLevels) && in_array($this->item->catAccess, $userAccessLevels);
					}
				}
			}
			else
			{
				throw new Exception('Helloworld id not found', 404);
			}
		}
		return $this->item;
	}

	public function getMapParams()
	{
		if ($this->item) 
		{
			$url = HelloworldHelperRoute::getAjaxURL();
			$this->mapParams = array(
				'latitude' => $this->item->latitude,
				'longitude' => $this->item->longitude,
				'zoom' => 10,
				'greeting' => $this->item->greeting,
				'ajaxurl' => $url
			);
			return $this->mapParams; 
		}
		else
		{
			throw new Exception('No helloworld details available for map', 500);
		}
	}

	public function getMapSearchResults($mapbounds)
	{
		try 
		{
			$db    = JFactory::getDbo();
			$query = $db->getQuery(true);
			$query->select('h.id, h.alias, h.catid, h.greeting, h.latitude, h.longitude, h.access')
			   ->from('#__helloworld as h')
			   ->where('h.latitude > ' . $mapbounds['minlat'] . 
				' AND h.latitude < ' . $mapbounds['maxlat'] .
				' AND h.longitude > ' . $mapbounds['minlng'] .
				' AND h.longitude < ' . $mapbounds['maxlng']);

			if (JLanguageMultilang::isEnabled())
			{
				$lang = JFactory::getLanguage()->getTag();
				$query->where('h.language IN ("*","' . $lang . '")');
			}

			$user = JFactory::getUser();
			$loggedIn = $user->get('guest') != 1;
			if ($loggedIn && !$user->authorise('core.admin'))
			{
				$userAccessLevels = $user->getAuthorisedViewLevels();
				$query->where('h.access IN (' . implode(",", $userAccessLevels) . ')');
				$query->join('LEFT', $db->quoteName('#__categories', 'c') . ' ON c.id = h.catid');
				$query->where('(c.access IN (' . implode(",", $userAccessLevels) . ') OR h.catid = 0)');
			}

			$db->setQuery($query);
			$results = $db->loadObjectList(); 
		}
		catch (Exception $e)
		{
			$msg = $e->getMessage();
			JFactory::getApplication()->enqueueMessage($msg, 'error'); 
			$results = null;
		}

		if (JLanguageMultilang::isEnabled())
		{
			$query_lang = "&lang={$lang}";
		}
		else
		{
			$query_lang = "";
		}

		for ($i = 0; $i < count($results); $i++) 
		{
			$results[$i]->url = JRoute::_('index.php?option=com_helloworld&view=helloworld&id=' . $results[$i]->id . 
				":" . $results[$i]->alias . '&catid=' . $results[$i]->catid . $query_lang);
		}

		return $results; 
	}

	public function getChildren($id)
	{
		$table = $this->getTable();
		$children = $table->getTree($id);
		return $children;
	}
}

In the view we handle the case of canAccess being false. Note that there is a problem with Joomla's redirect functionality here. We provide a redirect to the com_users login form, and specify the url to access after logging in within the "return" parameter, as described in How do you redirect users after a successful login. However, if the user enters the credentials into the Login Form module instead then that module encodes the return parameter based on a url which has already the return parameter set and it doesn't work. So ideally we either have to

omit the redirect to the com_users login form, and just assume the user will enter the details in the login module box, or,
redirect to the com_users login form, but we should find a means of removing the login module from that page (eg by redirecting to a specific hidden menuitem which displays the login form, but on which the login module is absent).

site/views/helloworld/view.html.php

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */

// No direct access to this file
defined('_JEXEC') or die('Restricted access');

/**
 * HTML View class for the HelloWorld Component
 *
 * @since  0.0.1
 */
class HelloWorldViewHelloWorld extends JViewLegacy
{
	/**
	 * Display the Hello World view
	 *
	 * @param   string  $tpl  The name of the template file to parse; automatically searches through the template paths.
	 *
	 * @return  void
	 */
	function display($tpl = null)
	{
		// Assign data to the view
		$this->item = $this->get('Item');
		$user = JFactory::getUser();
		$app = JFactory::getApplication();

		// Check for errors.
		if (count($errors = $this->get('Errors')))
		{
			JLog::add(implode('<br />', $errors), JLog::WARNING, 'jerror');

			return false;
		}

		// Take action based on whether the user has access to see the record or not
		$loggedIn = $user->get('guest') != 1;
		if (!$this->item->canAccess)
		{
			if ($loggedIn)
			{
				$app->enqueueMessage(JText::_('JERROR_ALERTNOAUTHOR'), 'error');
				$app->setHeader('status', 403, true);
				return;
			}
			else
			{
				$return = base64_encode(JUri::getInstance());
				$login_url_with_return = JRoute::_('index.php?option=com_users&return=' . $return, false);
				$app->enqueueMessage(JText::_('COM_HELLOWORLD_MUST_LOGIN'), 'notice');
				$app->redirect($login_url_with_return, 403);
			}
		}

		$this->addMap();

		$tagsHelper = new JHelperTags;
		$this->item->tags = $tagsHelper->getItemTags('com_helloworld.helloworld' , $this->item->id);

		$model = $this->getModel();
		$this->parentItem = $model->getItem($this->item->parent_id);
		$this->children = $model->getChildren($this->item->id);
		// getChildren includes the record itself (as well as the children) so remove this record
		unset($this->children[0]);

		// Display the view
		parent::display($tpl);
	}

	function addMap() 
	{
		$document = JFactory::getDocument();

		// everything's dependent upon JQuery
		JHtml::_('jquery.framework');

		// we need the Openlayers JS and CSS libraries
		$document->addScript("https://cdnjs.cloudflare.com/ajax/libs/openlayers/4.6.4/ol.js");
		$document->addStyleSheet("https://cdnjs.cloudflare.com/ajax/libs/openlayers/4.6.4/ol.css");

		// ... and our own JS and CSS
		$document->addScript(JURI::root() . "media/com_helloworld/js/openstreetmap.js");
		$document->addStyleSheet(JURI::root() . "media/com_helloworld/css/openstreetmap.css");

		// get the data to pass to our JS code
		$params = $this->get("mapParams");
		$document->addScriptOptions('params', $params);
	}
}

Frontend Category Display

In the category model we post-process the helloworld records which have the specified category id, and for the records which the user can't access, we either remove them completely from the list (if the user is already logged in) or set the item canAccess property to false (if the user isn't logged in). Note that by default the JCategories methods which we use here remove records to which the user doesn't have access, so we specify in the constructor the options array set to array('access' => false) so that all records are returned, and we perform the access checks ourselves.

site/models/category.php

<?php
/**
 * Model for displaying the helloworld messages in a given category
 */

defined('_JEXEC') or die;

class HelloworldModelCategory extends JModelList
{
	public function __construct($config = array())
	{
		if (empty($config['filter_fields']))
		{
			$config['filter_fields'] = array(
				'id',
				'greeting',
				'alias',
				'lft',
			);
		}

		parent::__construct($config);
	}
    
	protected function populateState($ordering = null, $direction = null)
	{
		parent::populateState($ordering, $direction);
        
		$app = JFactory::getApplication('site');
		$catid = $app->input->getInt('id');

		$this->setState('category.id', $catid);
	}
    
	protected function getListQuery()
	{
		$db    = JFactory::getDbo();
		$query = $db->getQuery(true);

		$catid = $this->getState('category.id'); 
		$query->select('id, greeting, alias, catid, access')
			->from($db->quoteName('#__helloworld'))
			->where('catid = ' . $catid);

		if (JLanguageMultilang::isEnabled())
		{
			$lang = JFactory::getLanguage()->getTag();
			$query->where('language IN ("*","' . $lang . '")');
		}

		$orderCol	= $this->state->get('list.ordering', 'lft');
		$orderDirn 	= $this->state->get('list.direction', 'asc');

		$query->order($db->escape($orderCol) . ' ' . $db->escape($orderDirn));

		return $query;	
	}

	public function getCategoryName()
	{
		$catid = $this->getState('category.id'); 
		$categories = JCategories::getInstance('Helloworld', array('access' => false));
		$categoryNode = $categories->get($catid);   
		return $categoryNode->title; 
	}
    
	public function getSubcategories()
	{
		$catid = $this->getState('category.id'); 
		$categories = JCategories::getInstance('Helloworld', array('access' => false));
		$categoryNode = $categories->get($catid);
		$subcats = $categoryNode->getChildren(); 
        
		$lang = JFactory::getLanguage()->getTag();
		if (JLanguageMultilang::isEnabled() && $lang)
		{
			$query_lang = "&lang={$lang}";
		}
		else
		{
			$query_lang = '';
		}
        
		foreach ($subcats as $subcat)
		{
			$subcat->url = JRoute::_("index.php?view=category&id=" . $subcat->id . $query_lang);
		}
		return $subcats;
	}

	public function getCategoryAccess()
	{
		$catid = $this->getState('category.id'); 
		$categories = JCategories::getInstance('Helloworld', array('access' => false));
		$categoryNode = $categories->get($catid);   
		return $categoryNode->access; 
	}
	
	public function getItems()
	{
		$items = parent::getItems();
		$user = JFactory::getUser();
		$loggedIn = $user->get('guest') != 1;

		if ($user->authorise('core.admin')) // ie superuser
		{
			return $items;
		}
		else
		{
			$userAccessLevels = $user->getAuthorisedViewLevels();
			$catAccess = $this->getCategoryAccess();
			
			if (!in_array($catAccess, $userAccessLevels))
			{  // the user hasn't access to the category
				if ($loggedIn)
				{	
					return array();
				}
				else
				{
					foreach ($items as $item)
					{
						$item->canAccess = false;
					}
					return $items;
				}
			}

			foreach ($items as $item) 
			{
				if (!in_array($item->access, $userAccessLevels))
				{
					if ($loggedIn)
					{
						unset($item);
					}
					else
					{
						$item->canAccess = false;
					}
				}
			}
		}
		return $items;
	}
}

In the category layout file we change the display if the canAccess flag is set to false.

site/views/category/tmpl/default.php

<?php
/**
 * Layout file for displaying helloworld messages belonging to a given category
 */

defined('_JEXEC') or die;

JHtml::_('formbehavior.chosen', 'select');

$listOrder     = $this->escape($this->state->get('list.ordering'));
$listDirn      = $this->escape($this->state->get('list.direction'));
$lang = JFactory::getLanguage()->getTag();
if (JLanguageMultilang::isEnabled() && $lang)
{
    $query_lang = "&lang={$lang}";
}
else
{
    $query_lang = "";
}
?>
<form action="#" method="post" id="adminForm" name="adminForm">
<h1><?php echo $this->categoryName; ?></h1>
<div id="j-main-container" class="span10">
    <div class="row-fluid">
        <div class="span10">
            <?php
                echo JLayoutHelper::render(
                    'joomla.searchtools.default',
                    array('view' => $this, 'searchButton' => false)
                );
            ?>
        </div>
    </div>
<table class="table table-striped table-hover">
    <thead>
    <tr>
        <th width="5%"><?php echo JText::_('JGLOBAL_NUM'); ?></th>
        <th width="20%">
            <?php echo JHtml::_('searchtools.sort', 'COM_HELLOWORLD_HELLOWORLD_GREETING_LABEL', 'greeting', $listDirn, $listOrder); ?>
        </th>
        <th width="20%">
            <?php echo JHtml::_('searchtools.sort', 'COM_HELLOWORLD_HELLOWORLD_ALIAS_LABEL', 'alias', $listDirn, $listOrder); ?>
        </th>
        <th width="20%">
            <?php echo JText::_('COM_HELLOWORLD_HELLOWORLD_FIELD_URL_LABEL'); ?>
        </th>
        <th width="5%">
            <?php echo JHtml::_('searchtools.sort', 'JGLOBAL_FIELD_ID_LABEL', 'id', $listDirn, $listOrder); ?>
        </th>
    </tr>
    </thead>
    <tfoot>
        <tr>
            <td colspan="5">
                <?php echo $this->pagination->getListFooter(); ?>
            </td>
        </tr>
    </tfoot>
    <tbody>
        <?php if (!empty($this->items)) : ?>
            <?php foreach ($this->items as $i => $row) : 
                if (isset($row->canAccess) && !$row->canAccess) : ?>
                    <tr>
                        <td align="center" colspan="5"><?php echo $row->greeting . " - " . JText::_('COM_HELLOWORLD_MUST_LOGIN'); ?></td>
                    </tr>
                <?php else :
                    $url = JRoute::_('index.php?option=com_helloworld&view=helloworld&id=' . $row->id . ':' . $row->alias . '&catid=' . $row->catid . $query_lang);
                    ?>
                    <tr>
                        <td align="center"><?php echo $this->pagination->getRowOffset($i); ?></td>
                        <td align="center"><?php echo $row->greeting; ?></td>
                        <td align="center"><?php echo $row->alias; ?></td>
                        <td align="center"><a href="<?php echo $url; ?>"><?php echo $url; ?></a></td>
                        <td align="center"><?php echo $row->id; ?></td>
                    </tr>
                <?php endif; ?>
            <?php endforeach; ?>
        <?php endif; ?>
    </tbody>
</table>
<h1><?php echo JText::_('COM_HELLOWORLD_HEADER_SUBCATEGORIES'); ?></h1>
<?php foreach ($this->subcategories as $subcategory) : ?>
    <h3><a href="<?php echo $subcategory->url; ?>"> <?php echo $subcategory->title; ?> </a></h3>
    <p><?php echo $subcategory->description; ?></p>
<?php endforeach; ?>
</div>
</form>

Updated Language Strings

admin/language/en-GB/en-GB.com_helloworld.ini

; Joomla! Project
; Copyright (C) 2005 - 2018 Open Source Matters. All rights reserved.
; License GNU General Public License version 2 or later; see LICENSE.txt, see LICENSE.php
; Note : All ini files need to be saved as UTF-8

COM_HELLOWORLD_ADMINISTRATION="HelloWorld - Administration"
COM_HELLOWORLD_ADMINISTRATION_CATEGORIES="HelloWorld - Categories"
COM_HELLOWORLD_NUM="#"
COM_HELLOWORLD_HELLOWORLDS_FILTER="Filters"
COM_HELLOWORLD_AUTHOR="Author"
COM_HELLOWORLD_LANGUAGE="Language"
COM_HELLOWORLD_CREATED_DATE="Created"
COM_HELLOWORLD_PUBLISHED="Published"
COM_HELLOWORLD_HELLOWORLDS_NAME="Name"
COM_HELLOWORLD_HELLOWORLDS_POSITION="Position"
COM_HELLOWORLD_HELLOWORLDS_IMAGE="Image"
COM_HELLOWORLD_HELLOWORLDS_ASSOCIATIONS="Associations"
COM_HELLOWORLD_ID="Id"

COM_HELLOWORLD_HELLOWORLD_CREATING="HelloWorld - Creating"
COM_HELLOWORLD_HELLOWORLD_DETAILS="Details"
COM_HELLOWORLD_HELLOWORLD_EDITING="HelloWorld - Editing"
COM_HELLOWORLD_HELLOWORLD_ERROR_UNACCEPTABLE="Some values are unacceptable"
COM_HELLOWORLD_HELLOWORLD_FIELD_CATID_DESC="The category the messages belongs to"
COM_HELLOWORLD_HELLOWORLD_FIELD_CATID_LABEL="Category"
COM_HELLOWORLD_HELLOWORLD_FIELD_GREETING_DESC="This message will be displayed"
COM_HELLOWORLD_HELLOWORLD_FIELD_GREETING_LABEL="Message"
COM_HELLOWORLD_HELLOWORLD_FIELD_DESCRIPTION_DESC="Message description"
COM_HELLOWORLD_HELLOWORLD_FIELD_DESCRIPTION_LABEL="Description"
COM_HELLOWORLD_HELLOWORLD_FIELD_SHOW_CATEGORY_LABEL="Show category"
COM_HELLOWORLD_HELLOWORLD_FIELD_SHOW_CATEGORY_DESC="If set to Show, the title of the message&rsquo;s category will show."
COM_HELLOWORLD_HELLOWORLD_FIELD_LATITUDE_LABEL="Latitude"
COM_HELLOWORLD_HELLOWORLD_FIELD_LATITUDE_DESC="Enter the position latitude, between -90 and +90 degrees"
COM_HELLOWORLD_HELLOWORLD_FIELD_LONGITUDE_LABEL="Longitude"
COM_HELLOWORLD_HELLOWORLD_FIELD_LONGITUDE_DESC="Enter the position longitude, between -180 and +180 degrees"
COM_HELLOWORLD_HELLOWORLD_FIELD_PARENT_LABEL="Parent"
COM_HELLOWORLD_HELLOWORLD_FIELD_PARENT_DESC="Select the parent record"
COM_HELLOWORLD_ITEM_FIELD_ORDERING_VALUE_FIRST="-- First record"
COM_HELLOWORLD_ITEM_FIELD_ORDERING_VALUE_LAST="-- Last record"
COM_HELLOWORLD_ITEM_FIELD_ORDERING_TEXT="Ordering will be available after saving."
COM_HELLOWORLD_HELLOWORLD_FIELD_LANGUAGE_DESC="Select the appropriate language"
COM_HELLOWORLD_IMAGE_FIELDS="Image details"
COM_HELLOWORLD_HELLOWORLD_FIELD_IMAGE_LABEL="Select image"
COM_HELLOWORLD_HELLOWORLD_FIELD_IMAGE_DESC="Select an image from the library, or upload a new one"
COM_HELLOWORLD_HELLOWORLD_FIELD_ALT_LABEL="Alt text"
COM_HELLOWORLD_HELLOWORLD_FIELD_ALT_DESC="Alternative text (if image cannot be displayed)"
COM_HELLOWORLD_HELLOWORLD_FIELD_CAPTION_LABEL="Caption"
COM_HELLOWORLD_HELLOWORLD_FIELD_CAPTION_DESC="Provide a caption for the image"
COM_HELLOWORLD_HELLOWORLD_HEADING_GREETING="Greeting"
COM_HELLOWORLD_HELLOWORLD_HEADING_ID="Id"
COM_HELLOWORLD_MANAGER_HELLOWORLD_EDIT="HelloWorld manager: Edit Message"
COM_HELLOWORLD_MANAGER_HELLOWORLD_NEW="HelloWorld manager: New Message"
COM_HELLOWORLD_MANAGER_HELLOWORLDS="HelloWorld manager"
COM_HELLOWORLD_EDIT_HELLOWORLD="Edit message"
COM_HELLOWORLD_N_ITEMS_DELETED_1="One message deleted"
COM_HELLOWORLD_N_ITEMS_DELETED_MORE="%d messages deleted"
COM_HELLOWORLD_N_ITEMS_PUBLISHED="%d message(s) published"
COM_HELLOWORLD_N_ITEMS_UNPUBLISHED="%d message(s) unpublished"
COM_HELLOWORLD_HELLOWORLD_GREETING_LABEL="Greeting"
COM_HELLOWORLD_HELLOWORLD_GREETING_DESC="Add Hello World Greeting"
COM_HELLOWORLD_SUBMENU_MESSAGES="Messages"
COM_HELLOWORLD_SUBMENU_CATEGORIES="Categories"
COM_HELLOWORLD_CONFIGURATION="HelloWorld Configuration"
COM_HELLOWORLD_CONFIG_GREETING_SETTINGS_LABEL="Messages settings"
COM_HELLOWORLD_CONFIG_GREETING_SETTINGS_DESC="Settings that will be applied to all messages by default"
COM_HELLOWORLD_HELLOWORLD_FIELD_CAPTCHA_LABEL="Captcha"
COM_HELLOWORLD_HELLOWORLD_FIELD_CAPTCHA_DESC="Select Captcha to use on front end form"
COM_HELLOWORLD_HELLOWORLD_FIELD_USER_TO_EMAIL_LABEL="User to email"
COM_HELLOWORLD_HELLOWORLD_FIELD_USER_TO_EMAIL_DESC="Select user to email when a new message is entered on front end"
COM_HELLOWORLD_FIELDSET_RULES="Message Permissions"
COM_HELLOWORLD_FIELD_RULES_LABEL="Permissions"
COM_HELLOWORLD_ACCESS_DELETE_DESC="Is this group allowed to edit this message?"
COM_HELLOWORLD_ACCESS_DELETE_DESC="Is this group allowed to delete this message?"
COM_HELLOWORLD_TAB_NEW_MESSAGE="New Message"
COM_HELLOWORLD_TAB_EDIT_MESSAGE="Message Details"
COM_HELLOWORLD_TAB_PARAMS="Parameters"
COM_HELLOWORLD_TAB_ASSOCIATIONS="Associations"
COM_HELLOWORLD_TAB_PERMISSIONS="Permissions"
COM_HELLOWORLD_TAB_IMAGE="Image"
COM_HELLOWORLD_LEGEND_DETAILS="Message Details"
COM_HELLOWORLD_LEGEND_PARAMS="Message Parameters"
COM_HELLOWORLD_LEGEND_ASSOCIATIONS="Message Associations"
COM_HELLOWORLD_LEGEND_PERMISSIONS="Message Permissions"
COM_HELLOWORLD_LEGEND_IMAGE="Image info"
; Column ordering in the Helloworlds view
COM_HELLOWORLD_ORDERING_ASC="Ordering ascending"
COM_HELLOWORLD_ORDERING_DESC="Ordering descending"
COM_HELLOWORLD_GREETING_ASC="Greeting ascending"
COM_HELLOWORLD_GREETING_DESC="Greeting descending"
COM_HELLOWORLD_AUTHOR_ASC="Author ascending"
COM_HELLOWORLD_AUTHOR_DESC="Author descending"
COM_HELLOWORLD_CREATED_ASC="Creation date ascending"
COM_HELLOWORLD_CREATED_DESC="Creation date descending"
COM_HELLOWORLD_PUBLISHED_ASC="Unpublished first"
COM_HELLOWORLD_PUBLISHED_DESC="Published first"
COM_HELLOWORLD_LANGUAGE_ASC="Language ascending"
COM_HELLOWORLD_LANGUAGE_DESC="Language descending"
COM_HELLOWORLD_ASSOCIATION_ASC="Association ascending"
COM_HELLOWORLD_ASSOCIATION_DESC="Association descending"
COM_HELLOWORLD_ACCESS_ASC="Access ascending"
COM_HELLOWORLD_ACCESS_DESC="Access descending"
; Helloworld menuitem - selecting a greeting via modal
COM_HELLOWORLD_MENUITEM_SELECT_MODAL_TITLE="Select greeting"
COM_HELLOWORLD_MENUITEM_SELECT_HELLOWORLD="Select"
COM_HELLOWORLD_MENUITEM_SELECT_BUTTON_TOOLTIP="Select a helloworld greeting"
; Checking in records
COM_HELLOWORLD_N_ITEMS_CHECKED_IN_0="No records checked in."
COM_HELLOWORLD_N_ITEMS_CHECKED_IN_1="%d record successfully checked in."
COM_HELLOWORLD_N_ITEMS_CHECKED_IN_MORE="%d records successfully checked in."

site/language/en-GB/en-GB.com_helloworld.ini

; add new message form
COM_HELLOWORLD_LEGEND_DETAILS="New Helloworld Message Details"
COM_HELLOWORLD_HELLOWORLD_CREATING="Add message"
COM_HELLOWORLD_HELLOWORLD_ERROR_UNACCEPTABLE="Sorry, you have an error"
COM_HELLOWORLD_HELLOWORLD_DETAILS="Message details"
COM_HELLOWORLD_HELLOWORLD_GREETING_LABEL="Greeting"
COM_HELLOWORLD_HELLOWORLD_GREETING_DESC="Please specify the greeting to add"
COM_HELLOWORLD_HELLOWORLD_GREETING_HINT="Any characters allowed"
COM_HELLOWORLD_HELLOWORLD_FIELD_CATID_LABEL="Category"
COM_HELLOWORLD_HELLOWORLD_FIELD_CATID_DESC="Please select the associated category"
COM_HELLOWORLD_HELLOWORLD_MESSAGE_LABEL="Reason"
COM_HELLOWORLD_HELLOWORLD_MESSAGE_DESC="Please say why you're adding this greeting"
COM_HELLOWORLD_HELLOWORLD_MESSAGE_HINT="No HTML tags!"
COM_HELLOWORLD_HELLOWORLD_FIELD_CAPTCHA_LABEL="Spam protection"
COM_HELLOWORLD_HELLOWORLD_FIELD_CAPTCHA_DESC="Prove you're a real person!"
COM_HELLOWORLD_HELLOWORLD_FIELD_SHOW_CATEGORY_LABEL="Display category or not?"
COM_HELLOWORLD_HELLOWORLD_FIELD_SHOW_CATEGORY_DESC="Select if you want the category displayed too"
COM_HELLOWORLD_HELLOWORLD_IMAGE_LABEL="Image information"
COM_HELLOWORLD_HELLOWORLD_PICTURE_LABEL="Image file to upload"
COM_HELLOWORLD_HELLOWORLD_PICTURE_DESC="Select the file with the image to upload"
COM_HELLOWORLD_HELLOWORLD_CAPTION_LABEL="Caption"
COM_HELLOWORLD_HELLOWORLD_CAPTION_DESC="Text to use as a caption for the image"
COM_HELLOWORLD_HELLOWORLD_ALTTEXT_LABEL="Alt text"
COM_HELLOWORLD_HELLOWORLD_ALTTEXT_DESC="Text to display if image cannot be shown"
COM_HELLOWORLD_HELLOWORLD_FIELD_PARENT_LABEL="Parent"
COM_HELLOWORLD_HELLOWORLD_FIELD_PARENT_DESC="Select the record which is to be the parent"
; save and cancel confirmation messages
COM_HELLOWORLD_ADD_SUCCESSFUL="New greeting successfully saved"
COM_HELLOWORLD_ADD_CANCELLED="New greeting cancelled ok"
; file upload error conditions
COM_HELLOWORLD_ERROR_FILEUPLOAD="PHP Error %s encountered when uploading file"
COM_HELLOWORLD_ERROR_FILETOOLARGE="Upload file exceeds max size configured in Joomla"
COM_HELLOWORLD_ERROR_BADFILENAME="Upload file has an invalid filename"
COM_HELLOWORLD_ERROR_FILE_EXISTS="Upload file already exists"
COM_HELLOWORLD_ERROR_UNABLE_TO_UPLOAD_FILE="Error creating uploaded file"
; helloworld greeting page
COM_HELLOWORLD_PARENT="Parent"
COM_HELLOWORLD_CHILDREN="Children"
COM_HELLOWORLD_SEARCH_HERE_BUTTON="Search here"
; Ajax handling errors
COM_HELLOWORLD_ERROR_NO_RECORDS="Didn't get any records"
COM_HELLOWORLD_ERROR_NO_MAP_BOUNDS="Error: no map bounds"
; category view, search and ordering fields and headings
COM_HELLOWORLD_SORT_BY="Sort by ..."
COM_HELLOWORLD_ORDERING_ASC="Ordering asc"
COM_HELLOWORLD_ORDERING_DESC="Ordering desc"
COM_HELLOWORLD_GREETING_ASC="Greeting asc"
COM_HELLOWORLD_GREETING_DESC="Greeting desc"
COM_HELLOWORLD_ID_ASC="id asc"
COM_HELLOWORLD_ID_DESC="id desc"
COM_HELLOWORLD_ALIAS_ASC="alias asc"
COM_HELLOWORLD_ALIAS_DESC="alias desc"
COM_HELLOWORLD_HELLOWORLD_ALIAS_LABEL="Alias"
COM_HELLOWORLD_HELLOWORLD_FIELD_URL_LABEL="URL"
COM_HELLOWORLD_HEADER_SUBCATEGORIES="Subcategories"
; Access errors
COM_HELLOWORLD_MUST_LOGIN="You must login before trying to view this item"

Packaging the Component

Contents of your code directory. Each file link below takes you to the step in the tutorial which has the latest version of that source code file.

helloworld.xml

<?xml version="1.0" encoding="utf-8"?>
<extension type="component" version="3.0" method="upgrade">

	<name>COM_HELLOWORLD</name>
	<!-- The following elements are optional and free of formatting constraints -->
	<creationDate>January 2018</creationDate>
	<author>John Doe</author>
	<authorEmail>john.doe@example.org</authorEmail>
	<authorUrl>http://www.example.org</authorUrl>
	<copyright>Copyright Info</copyright>
	<license>License Info</license>
	<!--  The version string is recorded in the components table -->
	<version>0.0.29</version>
	<!-- The description is optional and defaults to the name -->
	<description>COM_HELLOWORLD_DESCRIPTION</description>

	<!-- Runs on install/uninstall/update; New in 2.5 -->
	<scriptfile>script.php</scriptfile>

	<install> <!-- Runs on install -->
		<sql>
			<file driver="mysql" charset="utf8">sql/install.mysql.utf8.sql</file>
		</sql>
	</install>
	<uninstall> <!-- Runs on uninstall -->
		<sql>
			<file driver="mysql" charset="utf8">sql/uninstall.mysql.utf8.sql</file>
		</sql>
	</uninstall>
	<update> <!-- Runs on update; New since J2.5 -->
		<schemas>
			<schemapath type="mysql">sql/updates/mysql</schemapath>
		</schemas>
	</update>

	<!-- Site Main File Copy Section -->
	<!-- Note the folder attribute: This attribute describes the folder
		to copy FROM in the package to install therefore files copied
		in this section are copied from /site/ in the package -->
	<files folder="site">
		<filename>index.html</filename>
		<filename>helloworld.php</filename>
		<filename>controller.php</filename>
		<filename>router.php</filename>
		<folder>controllers</folder>
		<folder>views</folder>
		<folder>models</folder>
		<folder>helpers</folder>
	</files>

		<languages folder="site/language">
			<language tag="en-GB">en-GB/en-GB.com_helloworld.ini</language>
			<language tag="fr-FR">fr-FR/fr-FR.com_helloworld.ini</language>
		</languages>

	<media destination="com_helloworld" folder="media">
		<filename>index.html</filename>
		<folder>images</folder>
		<folder>js</folder>
		<folder>css</folder>
	</media>

	<administration>
		<!-- Administration Menu Section -->
		<menu link='index.php?option=com_helloworld' img="../media/com_helloworld/images/tux-16x16.png">COM_HELLOWORLD_MENU</menu>
		<!-- Administration Main File Copy Section -->
		<!-- Note the folder attribute: This attribute describes the folder
			to copy FROM in the package to install therefore files copied
			in this section are copied from /admin/ in the package -->
		<files folder="admin">
			<!-- Admin Main File Copy Section -->
			<filename>index.html</filename>
			<filename>config.xml</filename>
			<filename>helloworld.php</filename>
			<filename>controller.php</filename>
			<filename>access.xml</filename>
			<!-- SQL files section -->
			<folder>sql</folder>
			<!-- tables files section -->
			<folder>tables</folder>
			<!-- models files section -->
			<folder>models</folder>
			<!-- views files section -->
			<folder>views</folder>
			<!-- controllers files section -->
			<folder>controllers</folder>
			<!-- helpers files section -->
			<folder>helpers</folder>
		</files>
		<languages folder="admin/language">
			<language tag="en-GB">en-GB/en-GB.com_helloworld.ini</language>
			<language tag="en-GB">en-GB/en-GB.com_helloworld.sys.ini</language>
			<language tag="fr-FR">fr-FR/fr-FR.com_helloworld.ini</language>
			<language tag="fr-FR">fr-FR/fr-FR.com_helloworld.sys.ini</language>
		</languages>
	</administration>

</extension>

Contributors

Robbie Jackson

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J3.x

J3.x:Developing an MVC Component/Adding Access

From Joomla! Documentation

< J3.x:Developing an MVC Component
Revision as of 18:35, 21 March 2020 by FuzzyBot (talk | contribs) (Updating to match new version of source page)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

Introduction

Approach

Database Changes

Admin back end changes

Frontend changes

Database

Admin Edit Form

Admin Helloworlds Display

Front End Hello World Menuitem and Ajax Display

Frontend Category Display

Updated Language Strings

Packaging the Component

Contributors

J3.x

J3.x:Developing an MVC Component/Adding Access

From Joomla! Documentation

< J3.x:Developing an MVC ComponentRevision as of 18:35, 21 March 2020 by FuzzyBot (talk | contribs) (Updating to match new version of source page)(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

Introduction

Approach

Database Changes

Admin back end changes

Frontend changes

Database

Admin Edit Form

Admin Helloworlds Display

Front End Hello World Menuitem and Ajax Display

Frontend Category Display

Updated Language Strings

Packaging the Component

Contributors

< J3.x:Developing an MVC Component
Revision as of 18:35, 21 March 2020 by FuzzyBot (talk | contribs) (Updating to match new version of source page)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)