351 lines
9.6 KiB
Markdown
351 lines
9.6 KiB
Markdown
Plugin Development
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==================
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SamplePlugin.php
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----------------
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Each plugin requires a main class to interact with the GNU social system.
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The main class usually extends the Plugin class that comes with GNU social.
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The class has standard-named methods that will be called when certain events
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happen in the code base. These methods have names like 'onX' where X is an
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event name (see EVENTS.txt for the list of available events). Event handlers
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have pre-defined arguments, based on which event they're handling. A typical
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event handler:
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```php
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public function onSomeEvent($paramA, &$paramB): bool
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{
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if ($paramA == 'jed') {
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throw new Exception(sprintf(_m("Invalid parameter %s"), $paramA));
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}
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$paramB = 'spock';
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return true;
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}
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```
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Event Handlers
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--------------
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Event handlers must return a Boolean value.
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If they return false, all other event handlers for this event (in other plug-in)
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will be skipped, and in some cases the default processing for that event would
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be skipped. This is great for replacing the default action of an event.
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If the handler returns true, processing of other event handlers and the default
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processing will continue. This is great for extending existing functionality.
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If the handler throws an exception, processing will stop, and the exception's
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error will be shown to the user.
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Installation
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------------
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To enable a plugin (like the SamplePlugin), site admins add the following code to their
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config.php file:
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```php
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addPlugin('Sample');
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```
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Third Party Plugins must be installed in `local/plugins/{$name}/{$pluginclass}.php`
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Here, `{$name}` is the name of the plugin, like 'Sample', and `{$pluginclass}`
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is the name of the main class, like 'SamplePlugin'. Plugins that are part of
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the main GNU social distribution go in 'plugins' and third-party or local ones
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go in 'local'.
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Simple plugins can be implemented as a single plugin. Others are more complex
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and require additional plugins; these should use their own directory, like
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'local/plugins/{$name}/'. All files related to the plugin, including images,
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JavaScript, CSS, external libraries or PHP plugins should go in the plugin
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directory.
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Plugin Configuration
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--------------------
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Plugins are configured using public instance attributes. To set their values,
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site administrators use this syntax:
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```php
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addPlugin('Sample', ['attr1' => 'foo', 'attr2' => 'bar']);
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```
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The same plugin class can be initialized multiple times with different arguments:
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```php
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addPlugin('EmailNotify', ['sendTo' => 'evan@status.net']);
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addPlugin('EmailNotify', ['sendTo' => 'brionv@status.net']);
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```
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```php
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class SamplePlugin extends Plugin
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{
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public $attr1 = null;
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public $attr2 = null;
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}
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```
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Initialization
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--------------
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Plugins overload this method to do any initialization they need, like connecting
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to remote servers or creating paths or so on. @return bool hook value; true
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means continue processing, false means stop.
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```php
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public function initialize(): bool
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{
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return true;
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}
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```
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Clean Up
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--------
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Plugins overload this method to do any cleanup they need, like disconnecting from
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remote servers or deleting temp files or so on.
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```php
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public function cleanup(): bool
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{
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return true;
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}
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```
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Database schema setup
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---------------------
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Plugins can add their own tables to the GNU social database. Plugins should use
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GNU social's schema interface to add or delete tables. The ensureTable() method
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provides an easy way to ensure a table's structure and availability.
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By default, the schema is checked every time GNU social is run (say, when a Web
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page is hit). Admins can configure their systems to only check the schema when
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the checkschema.php script is run, greatly improving performance. However, they
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need to remember to run that script after installing or upgrading a plugin!
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```php
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public function onCheckSchema(): bool
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{
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$schema = Schema::get();
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// '''For storing user-submitted flags on profiles'''
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$schema->ensureTable('user_greeting_count',[
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new ColumnDef('user_id', 'integer', null, true, 'PRI'),
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new ColumnDef('greeting_count', 'integer')
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]
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);
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return true;
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}
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```
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Load related plugins when needed
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--------------------------------
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Most non-trivial plugins will require extra plugins to do their work. Typically
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these include data classes, action classes, widget classes, or external libraries.
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This method receives a class name and loads the PHP file related to that class.
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By tradition, action classes typically have files named for the action, all
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lower-case. Data classes are in files with the data class name, initial letter
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capitalized.
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Note that this method will be called for *all* overloaded classes, not just ones
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in this plugin! So, make sure to return true by default to let other plugins,
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and the core code, get a chance.
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```php
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public function onAutoload($cls): bool
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{
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$dir = __DIR__;
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switch ($cls)
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{
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case 'HelloAction':
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include_once $dir . '/' . strtolower(mb_substr($cls, 0, -6)) . '.php';
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return false;
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case 'User_greeting_count':
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include_once $dir . '/'.$cls.'.php';
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return false;
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default:
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return true;
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}
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}
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```
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Map URLs to actions
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-------------------
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This event handler lets the plugin map URLs on the site to actions (and thus an
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action handler class). Note that the action handler class for an action will be
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named 'FoobarAction', where action = 'foobar'. The class must be loaded in the
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onAutoload() method.
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```php
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public function onRouterInitialized($m): bool
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{
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$m->connect('main/hello',
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['action' => 'hello']);
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return true;
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}
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```
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Modify the default menu to link to our custom action
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-----------------------------------------------------
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Using event handlers, it's possible to modify the default UI for pages almost
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without limit. In this method, we add a menu item to the default primary menu
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for the interface to link to our action.
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Action Class
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------------
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The Action class provides a rich set of events to hook, as well as output methods.
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```php
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public function onEndPrimaryNav($action): bool
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{
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// '''common_local_url()''' gets the correct URL for the action name we provide
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$action->menuItem(common_local_url('hello'),
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_m('Hello'), _m('A warm greeting'), false, 'nav_hello');
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return true;
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}
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public function onPluginVersion(&$versions): bool
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{
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$versions[] = [
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'name' => 'Sample',
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'version' => GNUSOCIAL_VERSION,
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'author' => 'Brion Vibber, Evan Prodromou',
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'homepage' => 'http://example.org/plugin',
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'rawdescription' =>
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_m('A sample plugin to show basics of development for new hackers.')
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];
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return true;
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}
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```
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hello.php
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---------
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This section is taken directly from the 'hello.php'. ( plugins/Sample/hello.php )
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Give a warm greeting to our friendly user.
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This sample action shows some basic ways of doing output in an action class.
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Action classes have several output methods that they override from the parent class.
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```php
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class HelloAction extends Action
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{
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var $user = null;
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var $gc = null;
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}
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```
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Take arguments for running
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--------------------------
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This method is called first, and it lets the action class get all its arguments
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and validate them. It's also the time to fetch any relevant data from the database.
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Action classes should run parent::prepare(array $args = []) as the first line
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of this method to make sure the default argument-processing happens.
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```php
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public function prepare(array $args = []): bool
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{
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parent::prepare($args);
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$this->user = common_current_user();
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if (!empty($this->user)) {
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$this->gc = User_greeting_count::inc($this->user->id);
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}
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return true;
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}
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```
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Handle request
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--------------
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This is the main method for handling a request. Note that most preparation
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should be done in the prepare() method; by the time handle() is called the
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action should be more or less ready to go.
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```php
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public function handle(): void
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{
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parent::handle();
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$this->showPage();
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}
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```
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Title of this page
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------------------
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Override this method to show a custom title.
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```php
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public function title(): string
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{
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if (empty($this->user)) {
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return _m('Hello');
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} else {
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return sprintf(_m('Hello, %s'), $this->user->nickname);
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}
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}
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```
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Show content in the content area
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--------------------------------
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The default GNU social page has a lot of decorations: menus, logos, tabs, all
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that jazz. This method is used to show content in the content area of the
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page; it's the main thing you want to overload. This method also demonstrates
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use of a plural localized string.
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```php
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public function showContent(): void
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{
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if (empty($this->user)) {
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$this->element('p', ['class' => 'greeting'],
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_m('Hello, stranger!'));
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} else {
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$this->element('p', ['class' => 'greeting'],
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sprintf(_m('Hello, %s'), $this->user->nickname));
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$this->element('p', ['class' => 'greeting_count'],
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sprintf(_m('I have greeted you %d time.',
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'I have greeted you %d times.',
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$this->gc->greeting_count),
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$this->gc->greeting_count));
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}
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}
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```
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Return true if read only.
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-------------------------
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Some actions only read from the database; others read and write. The simple
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database load-balancer built into GNU social will direct read-only actions to
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database mirrors (if they are configured) and read-write actions to the master database.
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This defaults to false to avoid data integrity issues, but you should make sure
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to overload it for performance gains.
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```php
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public function isReadOnly($args): bool
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{
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return false;
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}
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```
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