artur
10 years ago
19 changed files with 349 additions and 259 deletions
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Application Components |
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====================== |
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Applications are [service locators](concept-service-locators.md). They host a set of the so-called |
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*application components* that provide different services for processing requests. For example, |
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the `urlManager` component is responsible for routing Web requests to appropriate controllers; |
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the `db` component provides DB-related services; and so on. |
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Each application component has an ID that uniquely identifies itself among other application components |
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in the same application. You can access an application component through the expression |
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```php |
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\Yii::$app->ComponentID |
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``` |
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For example, you can use `\Yii::$app->db` to get the [[yii\db\Connection|DB connection]], |
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and `\Yii::$app->cache` to get the [[yii\caching\Cache|primary cache]] registered with the application. |
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Application components can be any objects. You can register them by configuring |
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the [[yii\base\Application::components]] property in [application configurations](structure-applications.md#application-configurations). |
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For example, |
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```php |
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[ |
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'components' => [ |
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// register "cache" component using a class name |
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'cache' => 'yii\caching\ApcCache', |
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// register "db" component using a configuration array |
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'db' => [ |
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'class' => 'yii\db\Connection', |
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'dsn' => 'mysql:host=localhost;dbname=demo', |
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'username' => 'root', |
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'password' => '', |
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], |
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// register "search" component using an anonymous function |
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'search' => function () { |
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return new app\components\SolrService; |
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}, |
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], |
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] |
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``` |
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> Info: While you can register as many application components as you want, you should do this judiciously. |
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Application components are like global variables. Using too many application components can potentially |
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make your code harder to test and maintain. In many cases, you can simply create a local component |
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and use it when needed. |
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## Core Application Components <a name="core-application-components"></a> |
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Yii defines a set of *core* application components with fixed IDs and default configurations. For example, |
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the [[yii\web\Application::request|request]] component is used to collect information about |
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a user request and resolve it into a [route](runtime-routing.md); the [[yii\base\Application::db|db]] |
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component represents a database connection through which you can perform database queries. |
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It is with help of these core application components that Yii applications are able to handle user requests. |
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Below is the list of the predefined core application components. You may configure and customize them |
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like you do with normal application components. When you are configuring a core application component, |
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if you do not specify its class, the default one will be used. |
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* [[yii\web\AssetManager|assetManager]]: manages asset bundles and asset publishing. |
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Please refer to the [Managing Assets](output-assets.md) section for more details. |
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* [[yii\db\Connection|db]]: represents a database connection through which you can perform DB queries. |
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Note that when you configure this component, you must specify the component class as well as other required |
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component properties, such as [[yii\db\Connection::dsn]]. |
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Please refer to the [Data Access Objects](db-dao.md) section for more details. |
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* [[yii\base\Application::errorHandler|errorHandler]]: handles PHP errors and exceptions. |
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Please refer to the [Handling Errors](tutorial-handling-errors.md) section for more details. |
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* [[yii\base\Formatter|formatter]]: formats data when they are displayed to end users. For example, a number |
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may be displayed with thousand separator, a date may be formatted in long format. |
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Please refer to the [Data Formatting](output-formatting.md) section for more details. |
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* [[yii\i18n\I18N|i18n]]: supports message translation and formatting. |
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Please refer to the [Internationalization](tutorial-i18n.md) section for more details. |
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* [[yii\log\Dispatcher|log]]: manages log targets. |
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Please refer to the [Logging](tutorial-logging.md) section for more details. |
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* [[yii\swiftmailer\Mailer|mail]]: supports mail composing and sending. |
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Please refer to the [Mailing](tutorial-mailing.md) section for more details. |
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* [[yii\base\Application::response|response]]: represents the response being sent to end users. |
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Please refer to the [Responses](runtime-responses.md) section for more details. |
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* [[yii\base\Application::request|request]]: represents the request received from end users. |
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Please refer to the [Requests](runtime-requests.md) section for more details. |
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* [[yii\web\Session|session]]: represents the session information. This component is only available |
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in [[yii\web\Application|Web applications]]. |
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Please refer to the [Sessions and Cookies](runtime-sessions-cookies.md) section for more details. |
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* [[yii\web\UrlManager|urlManager]]: supports URL parsing and creation. |
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Please refer to the [URL Parsing and Generation](runtime-url-handling.md) section for more details. |
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* [[yii\web\User|user]]: represents the user authentication information. This component is only available |
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in [[yii\web\Application|Web applications]] |
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Please refer to the [Authentication](security-authentication.md) section for more details. |
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* [[yii\web\View|view]]: supports view rendering. |
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Please refer to the [Views](structure-views.md) section for more details. |
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You may apply some action filters to controller actions to accomplish tasks such as determining |
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who can access the current action, decorating the result of the action, etc. |
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An action filter is an instance of a class extending [[yii\base\ActionFilter]]. |
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To use an action filter, attach it as a behavior to a controller or a module. The following |
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example shows how to enable HTTP caching for the `index` action: |
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```php |
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public function behaviors() |
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{ |
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return [ |
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'httpCache' => [ |
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'class' => \yii\filters\HttpCache::className(), |
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'only' => ['index'], |
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'lastModified' => function ($action, $params) { |
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$q = new \yii\db\Query(); |
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return $q->from('user')->max('updated_at'); |
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}, |
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], |
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]; |
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} |
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``` |
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You may use multiple action filters at the same time. These filters will be applied in the |
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order they are declared in `behaviors()`. If any of the filter cancels the action execution, |
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the filters after it will be skipped. |
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When you attach a filter to a controller, it can be applied to all actions of that controller; |
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If you attach a filter to a module (or application), it can be applied to the actions of any controller |
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within that module (or application). |
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To create a new action filter, extend from [[yii\base\ActionFilter]] and override the |
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[[yii\base\ActionFilter::beforeAction()|beforeAction()]] and [[yii\base\ActionFilter::afterAction()|afterAction()]] |
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methods. The former will be executed before an action runs while the latter after an action runs. |
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The return value of [[yii\base\ActionFilter::beforeAction()|beforeAction()]] determines whether |
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an action should be executed or not. If `beforeAction()` of a filter returns false, the filters after this one |
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will be skipped and the action will not be executed. |
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The [authorization](authorization.md) section of this guide shows how to use the [[yii\filters\AccessControl]] filter, |
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and the [caching](caching.md) section gives more details about the [[yii\filters\PageCache]] and [[yii\filters\HttpCache]] filters. |
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These built-in filters are also good references when you learn to create your own filters. |
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