beforeAction()在Yii2中用于在控制器動作執(zhí)行前運行邏輯，如權限檢查或請求修改，必須返回true或父類調用以繼續(xù)執(zhí)行；afterAction()則在動作執(zhí)行后、響應發(fā)送前運行，適用于輸出修改或日志記錄。1. beforeAction()在動作執(zhí)行前運行，可用于用戶權限驗證，例如重定向未登錄用戶至登錄頁，需返回parent::beforeAction($action)或true以繼續(xù)流程，否則阻止動作執(zhí)行；2. 可通過檢查$action->id跳過特定動作的檢查；3. afterAction()在動作處理完成后運行，可修改動作結果或記錄日志，應返回parent::afterAction($action, $result)以確保正常響應流程。這些方法適用于影響多個動作的通用邏輯，如僅作用于單一動作則應直接在該動作中處理。

In Yii2, beforeAction() and afterAction() are two important methods you can use in your controllers to run logic before and after an action is executed. These are handy for tasks like authentication checks, logging, or modifying the request/response cycle.

What does beforeAction() do?

beforeAction() runs before a controller's action method (like actionIndex()) gets called. It gives you a chance to check things like user permissions, redirect unauthorized users, or modify the request.

For example, if you want to make sure a user is logged in before accessing certain pages:

public function beforeAction($action)
{
    if (Yii::$app->user->isGuest) {
        return $this->redirect(['site/login']);
    }
    return parent::beforeAction($action);
}

A few key points:

• You must return true or the parent call (parent::beforeAction($action)) to allow the action to continue.
• If you return false or a response object (like redirect()), it will stop the action from running.
• You can skip this check for specific actions by checking the $action->id.

Here’s how to skip it for login and error pages:

public function beforeAction($action)
{
    $allowedActions = ['login', 'error'];

    if (!in_array($action->id, $allowedActions) && Yii::$app->user->isGuest) {
        return $this->redirect(['site/login']);
    }

    return parent::beforeAction($action);
}

How about afterAction()?

afterAction() runs after the action has been processed but before the response is sent. This makes it useful for modifying output, logging execution time, or cleaning up resources.

Let’s say you want to log when an action finishes:

public function afterAction($action, $result)
{
    Yii::info("Action {$action->id} finished.");
    return parent::afterAction($action, $result);
}

Some things to note:

• The $result is whatever the action returns — usually a string or response object.
• You can modify $result before returning it.
• Like beforeAction(), you should return the result of parent::afterAction() unless you have a good reason not to.

When should you use these methods?

These methods are especially helpful when you're doing something that affects multiple actions, such as:

• Authentication and access control
• Request preprocessing
• Logging or profiling
• Modifying output globally

If the logic only applies to one action, it's better to handle it directly inside that action method instead.

That's basically it. They’re powerful but straightforward tools once you understand their flow and purpose. Just remember: always call the parent method unless you know exactly what you're doing.

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