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The manifest file in this example is very similar to that of normal components. Important contents for this example include:
Note the inclusion of the SQL folder in the administration files section. This tells Joomla to copy the contents of this folder to the web site during install or update. The schemapath declaration below depends on Joomla copying these files during the install or update process.
<administration> <files folder="admin"> <folder>sql</folder> </files> </administration>
This is the name of the component. The 'getParam($key)' method in the script.php file uses this value to identify the correct row in the extensions table. The manifest_cache field in the extensions table has the version string for the currently installed component.
Joomla stores this value in the manifest_cache field of the extensions table. The extensions table is where the custom code in the script.php file reads the version string of the currently installed component, and compares it to the version string of the update.
The custom component code uses this comparison to abort an update, if the version sequence is not allowed. Joomla also compares this string to the SQL update file names, to determine which SQL commands to execute.
This defines the directory that contains SQL files for component incremental database updates. You may choose to put the SQL files somewhere else in your component release, but make sure their location is documented here.
<update> <schemas> <schemapath type="mysql">sql/updates</schemapath> </schemas> </update>
The SQL files have a second function. In addition to potentially modifying the MySQL database, Joomla uses the names of these SQL files to update the version_id field in the #__schemas table for your component. It is important to have an SQL file for EVERY version of your component. The file should be empty if you have no SQL code to execute when updating to that version. You must have a file or the version_id will not get updated correctly. Joomla uses the version_id in the #__schemas table as the from version when calculating updates from an older version to a new version.
It is important to include these schemapath lines in your manifest file, even if you have no SQL commands to execute. By including these lines and including empty SQL files, the version_id value will be correctly maintained in the #__schemas table.
Here is the entire manifest file for version 1.0.
<?xml version="1.0" encoding="utf-8"?> <extension type="component" version="1.6" method="new"> <name>COM_DEMOCOMPUPDATE</name> <creationDate>2011 05 11</creationDate> <author>Your Name Here</author> <copyright>Free to copy</copyright> <license>none</license> <version>1.0</version> <description>Test the Install and Update Process</description> <!-- Runs on install/uninstall/update; New in 1.6 --> <scriptfile>script.php</scriptfile> <install> <sql> <file driver="mysql" charset="utf8">sql/install_data.sql</file> </sql> </install> <uninstall> <sql> <file driver="mysql" charset="utf8">sql/uninstall.sql</file> </sql> </uninstall> <update> <schemas> <schemapath type="mysql">sql/updates</schemapath> </schemas> </update> <files folder="site"> <filename>democompupdate.php</filename> <filename>controller.php</filename> <folder>models</folder> <folder>views</folder> </files> <administration> <files folder="admin"> <folder>sql</folder> </files> </administration> </extension>