MVC Anatomy: Getting Started
From Joomla! Documentation
Introduction[edit]
Joomla components follow the Model, View, Controller approach, or MVC for short. The Model is supposed to handle loading and storing of data. The View is supposed to handle display of data. And the Controller is supposed to handle program flow, the interaction between the component Model and View code.
If you want to build your own component there are two approaches to learning you might adopt:
- Build it step by step: by following a simple tutorial that describes each stage.
- Dissect it file by file: by taking a working component apart to learn how each part works.
This tutorial uses the latter approach. The component used for the tutorial is named com_countrybase. It is used to manage and display some basic data on the countries of the world. It is actually useful in its own right and could be used as a basis for building something more sophisticated.
Outline Objectives[edit]
Whatever your project you should start with an outline of your objectives and perhaps ask yourself whether those objectives can be attained with Joomla core components or an available extension. For com_countrybase a table of country data is needed, together with input and output pages. And perhaps a module to display a daily monetary exchange rate. And even a plugin called by a cli command to update currency data at regular intervals. This tutorial just covers the component.
The component needs a database table to store country data and a table to store currency data. Each will need a list view and an edit view. This is not something that can be accomplished with Joomla core components so it is clearly a case for a custom component.
Starter Tables[edit]
There is a lot of data about countries available from all sorts of sources in all sorts of formats. As there are at least 250 countries in the world, entering data for each country one by one using a data entry form would be quite tedious. So, I prepared starter tables by collecting data from several sources, combining them in a spreadsheet and then exporting sql statements to create the tables.
The data are based on ISO 3166 Country Codes but some very well-known countries are not included, for example England, Scotland and Wales. You do not need to worry about this. The tables are provided with the com_countrybase component. The table creation code in the component is described later.
The files for the com_countrybase component are available from Github:
https://github.com/ceford/j4xdemos-com-countrybase/archive/refs/heads/master.zip
Download and install the component to see it working in the Administrator menu. Create a menu item if you wish to see it working in your Site template. Also, unpack the zip file in your project file space, not in your test web-site tree. You can then examine the component file structure and file content with your favourite IDE or text edit tool.
Screenshot[edit]
This Administrator list of Countries has five items to minimise image size. Joomla normally displays 20 items.
Boilerplate Component[edit]
To help you get started with your own component there is a boilerplate component available from Github:
https://github.com/ceford/j4xdemos-com-bpsrc/archive/refs/heads/master.zip
Download and unpack this in your project file space, not in your test web-site tree. After download, make all the changes indicated in the README and you are ready to go.