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Modules |
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======= |
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Modules are self-contained software units that consist of [models](structure-models.md), [views](structure-views.md), |
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[controllers](structure-controllers.md), and other supporting components. End users can access the controllers |
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of a module when it is installed in [application](structure-applications.md). For these reasons, modules are |
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often viewed as mini-applications. Modules differ from [applications](structure-applications.md) in that |
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modules cannot be deployed alone and must reside within applications. |
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## Creating Modules <a name="creating-modules"></a> |
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A module is organized as a directory which is called the [[yii\base\Module::basePath|base path]] of the module. |
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Within the directory, there are sub-directories, such as `controllers`, `models`, `views`, which hold controllers, |
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models, views, and other code, just like in an application. The following example shows the content within a module: |
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``` |
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forum/ |
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Module.php the module class file |
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controllers/ containing controller class files |
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DefaultController.php the default controller class file |
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models/ containing model class files |
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views/ containing controller view and layout files |
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layouts/ containing layout view files |
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default/ containing view files for DefaultController |
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index.php the index view file |
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``` |
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### Module Classes <a name="module-classes"></a> |
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Each module should have a module class which extends from [[yii\base\Module]]. The class should be located |
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directly under the module's [[yii\base\Module::basePath|base path]] and should be [autoloadable](concept-autoloading.md). |
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When a module is being accessed, a single instance of the corresponding module class will be created. |
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Like [application instances](structure-applications.md), module instances are used to share data and components |
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for code within modules. |
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The following is an example how a module class may look like: |
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```php |
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namespace app\modules\forum; |
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class Module extends \yii\base\Module |
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{ |
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public function init() |
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{ |
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parent::init(); |
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$this->params['foo'] = 'bar'; |
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// ... other initialization code ... |
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} |
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} |
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``` |
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If the `init()` method contains a lot of code initializing the module's properties, you may also save them in terms |
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of a [configuration](concept-configurations.md) and load it with the following code in `init()`: |
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```php |
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public function init() |
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{ |
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parent::init(); |
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// initialize the module with the configuration loaded from config.php |
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\Yii::configure($this, require(__DIR__ . '/config.php')); |
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} |
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``` |
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where the configuration file `config.php` may contain the following content, similar to that in an |
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[application configuration](structure-applications.md#application-configurations). |
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```php |
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<?php |
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return [ |
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'components' => [ |
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// list of component configurations |
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], |
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'params' => [ |
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// list of parameters |
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], |
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]; |
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``` |
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### Controllers in Modules <a name="controllers-in-modules"></a> |
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When creating controllers in a module, a convention is to put the controller classes under the `controllers` |
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sub-namespace of the namespace of the module class. This also means the controller class files should be |
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put in the `controllers` directory within the module's [[yii\base\Module::basePath|base path]]. |
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For example, to create a `post` controller in the `forum` module shown in the last subsection, you should |
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declare the controller class like the following: |
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```php |
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namespace app\modules\forum\controllers; |
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use yii\web\Controller; |
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class PostController extends Controller |
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{ |
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// ... |
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} |
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``` |
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You may customize the namespace of controller classes by configuring the [[yii\base\Module::controllerNamespace]] |
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property. In case when some of the controllers are out of this namespace, you may make them accessible |
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by configuring the [[yii\base\Module::controllerMap]] property, similar to [what you do in an application](structure-applications.md#controller-map). |
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### Views in Modules <a name="views-in-modules"></a> |
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Views in a module should be put in the `views` directory within the module's [[yii\base\Module::basePath|base path]]. |
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For views rendered by a controller in the module, they should be put under the directory `views/ControllerID`, |
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where `ControllerID` refers to the [controller ID](structure-controllers.md#routes). For example, if |
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the controller class is `PostController`, the directory would be `views/post` within the module's |
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[[yii\base\Module::basePath|base path]]. |
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A module can specify a [layout](structure-views.md#layouts) that is applied to the views rendered by the module's |
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controllers. The layout should be put in the `views/layouts` directory by default, and you should configure |
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the [[yii\base\Module::layout]] property to point to the layout name. If you do not configure the `layout` property, |
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the application's layout will be used instead. |
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## Using Modules <a name="using-modules"></a> |
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To use a module in an application, simply configure the application by listing the module in |
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the [[yii\base\Application::modules|modules]] property of the application. The following code in the |
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[application configuration](structure-applications.md#application-configurations) uses the `forum` module: |
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```php |
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[ |
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'modules' => [ |
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'forum' => [ |
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'class' => 'app\modules\forum\Module', |
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// ... other configurations for the module ... |
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], |
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], |
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] |
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``` |
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The [[yii\base\Application::modules|modules]] property takes an array of module configurations. Each array key |
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represents a *module ID* which uniquely identifies the module among all modules in the application, and the corresponding |
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array value is a [configuration](concept-configurations.md) for creating the module. |
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### Routes <a name="routes"></a> |
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Like accessing controllers in an application, [routes](structure-controllers.md#routes) are used to address |
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controllers in a module. A route for a controller within a module must begin with the module ID followed by |
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the controller ID and action ID. For example, if an application uses a module named `forum`, then the route |
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`forum/post/index` would represent the `index` action of the `post` controller in the module. If the route |
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only contains the module ID, then the [[yii\base\Module::defaultRoute]] property, which defaults to `default`, |
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will determine which controller/action should be used. This means a route `forum` would represent the `default` |
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controller in the `forum` module. |
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### Accessing Modules <a name="accessing-modules"></a> |
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Within a module, you may often need to get the instance of the [module class](#module-classes) so that you can |
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access the module ID, module parameters, module components, etc. You can do so by using the following statement: |
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```php |
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$module = MyModuleClass::getInstance(); |
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``` |
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where `MyModuleClass` refers to the name of the module class that you are interested in. The `getInstance()` method |
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will return the currently requested instance of the module class. If the module is not requested, the method will |
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return null. Note that You do not want to manually create a new instance of the module class because it will be |
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different from the one created by Yii in response to a request. |
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> Info: When developing a module, you should not assume the module will use a fixed ID. This is because a module |
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can be associated with an arbitrary ID when used in an application or within another module. In order to get |
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the module ID, you should use the above approach to get the module instance first, and then get the ID via |
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`$module->id`. |
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You may also access the instance of a module using the following approaches: |
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```php |
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// get the module whose ID is "forum" |
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$module = \Yii::$app->getModule('forum'); |
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// get the module to which the currently requested controller belongs |
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$module = \Yii::$app->controller->module; |
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``` |
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The first approach is only useful when you know the module ID, while the second approach is best used when you |
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know about the controllers being requested. |
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Once getting hold of a module instance, you can access parameters or components registered with the module. For example, |
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```php |
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$maxPostCount = $module->params['maxPostCount']; |
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``` |
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### Bootstrapping Modules <a name="bootstrapping-modules"></a> |
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Some modules may need to be run for every request. The [[yii\debug\Module|debug]] module is such an example. |
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To do so, list the IDs of such modules in the [[yii\base\Application::bootstrap|bootstrap]] property of the application. |
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For example, the following application configuration makes sure the `debug` module is always load: |
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```php |
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[ |
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'bootstrap' => [ |
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'debug', |
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], |
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'modules' => [ |
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'debug' => 'yii\debug\Module', |
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], |
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] |
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``` |
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## Nested Modules <a name="nested-modules"></a> |
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Modules can be nested in unlimited levels. That is, a module can contain another module which can contain yet |
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another module. We call the former *parent module* while the latter *child module*. Child modules must be declared |
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in the [[yii\base\Module::modules|modules]] property of their parent modules. For example, |
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```php |
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namespace app\modules\forum; |
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class Module extends \yii\base\Module |
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{ |
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public function init() |
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{ |
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parent::init(); |
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$this->modules = [ |
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'admin' => [ |
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// you should consider using a shorter namespace here! |
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'class' => 'app\modules\forum\modules\admin\Module', |
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], |
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]; |
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} |
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} |
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``` |
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For a controller within a nested module, its route should include the IDs of all its ancestor module. |
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For example, the route `forum/admin/dashboard/index` represents the `index` action of the `dashboard` controller |
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in the `admin` module which is a child module of the `forum` module. |
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## Best Practices <a name="best-practices"></a> |
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Modules are best used in large applications whose features can be divided into several groups, each consisting of |
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a set of closely related features. Each such feature group can be developed as a module which is developed and |
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maintained by a specific developer or team. |
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Modules are also a good way of reusing code at the feature group level. Some commonly used features, such as |
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user management, comment management, can all be developed in terms of modules so that they can be reused easily |
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in future projects. |
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