授權

• 簡介

• Gate

  • 撰寫 Gate
  • 授權動作
  • Gate Response
  • 攔截 Gate 檢查
  • 內嵌授權

• 建立 Policy

  • 產生 Policy
  • 註冊 Policy

• 撰寫 Policy

  • Policy 方法
  • Policy Response
  • 不使用 Model 的方法
  • 訪客使用者
  • Policy 篩選器

• 通過 Policy 來授權動作

  • Via the User Model
  • Via the Gate Facade
  • 通過 Middleware
  • 通過 Blade 樣板
  • 提供額外的上下文

簡介

除了提供內建的認證服務，Laravel 也提供了一種能依給定資源來授權使用者的簡單功能。舉例來說，雖然使用者已登入，但這個使用者可能未被授權可更新或刪除網站所管理的特定的 Eloquent Model 或資料庫記錄。Laravel 的授權功能提供了一種簡單且有條理的方法來管理這些種類的授權。

Laravel 提供了兩種主要方法來授權動作：Gate 與 Policy。可以把 Gate 與 Policy 想成是路由與 Controller。Gate 提供了一種簡單、基於閉包的方法來進行授權；而 Policy 就像 Controller 一樣，可以將授權邏輯依照特定的 Model 或資源來進行分組。在本說明文件中，我們會先來探討 Gate，然後再來看看 Policy。

在製作應用程式時，不需要只使用 Gate 或只使用 Policy。大多數應用程式都在某種程度上組合使用 Gate 與 Policy，這樣完全沒問題！Gate 最適合用來處理與 Model 或資源沒關係的操作，如檢視管理員縱覽頁。相較之下，Policy 則應使用於想授權對特定 Model 或 Resource 的操作時

Gate

撰寫 Gate

Gates are simply closures that determine if a user is authorized to perform a given action. Typically, gates are defined within the boot method of the App\Providers\AppServiceProvider class using the Gate facade. Gates always receive a user instance as their first argument and may optionally receive additional arguments such as a relevant Eloquent model.

在此範例中，我們會定義一個用來判斷使用者能否更新給定 App\Models\Post Model 的 Gate。這個 Gate 會通過比對使用者的 id 與建立該貼文的 user_id 來進行判斷：

 1use App\Models\Post;
 2use App\Models\User;
 3use Illuminate\Support\Facades\Gate;
 4 
 5/**
 6 * Bootstrap any application services.
 7 */
 8public function boot(): void
 9{
10    Gate::define('update-post', function (User $user, Post $post) {
11        return $user->id === $post->user_id;
12    });
13}
 1use App\Models\Post;
 2use App\Models\User;
 3use Illuminate\Support\Facades\Gate;
 4 
 5/**
 6 * Bootstrap any application services.
 7 */
 8public function boot(): void
 9{
10    Gate::define('update-post', function (User $user, Post $post) {
11        return $user->id === $post->user_id;
12    });
13}

就像 Controller 一樣，Gate 也可以通過類別回呼陣列來定義：

 1use App\Policies\PostPolicy;
 2use Illuminate\Support\Facades\Gate;
 3 
 4/**
 5 * Bootstrap any application services.
 6 */
 7public function boot(): void
 8{
 9    Gate::define('update-post', [PostPolicy::class, 'update']);
10}
 1use App\Policies\PostPolicy;
 2use Illuminate\Support\Facades\Gate;
 3 
 4/**
 5 * Bootstrap any application services.
 6 */
 7public function boot(): void
 8{
 9    Gate::define('update-post', [PostPolicy::class, 'update']);
10}

授權動作

若要通過 Gate 來授權某個動作，可以使用 Gate Facade 提供的 allows 或 denies 方法。請注意，不需要將目前已登入的使用者傳給這幾個方法。Laravel 會自動處理好將使用者傳給 Gate 閉包。通常，我們會在 Controller 執行需要授權的特定動作前呼叫這些 Gate 授權方法：

 1<?php
 2 
 3namespace App\Http\Controllers;
 4 
 5use App\Http\Controllers\Controller;
 6use App\Models\Post;
 7use Illuminate\Http\RedirectResponse;
 8use Illuminate\Http\Request;
 9use Illuminate\Support\Facades\Gate;
10 
11class PostController extends Controller
12{
13    /**
14     * Update the given post.
15     */
16    public function update(Request $request, Post $post): RedirectResponse
17    {
18        if (! Gate::allows('update-post', $post)) {
19            abort(403);
20        }
21 
22        // Update the post...
23 
24        return redirect('/posts');
25    }
26}
 1<?php
 2 
 3namespace App\Http\Controllers;
 4 
 5use App\Http\Controllers\Controller;
 6use App\Models\Post;
 7use Illuminate\Http\RedirectResponse;
 8use Illuminate\Http\Request;
 9use Illuminate\Support\Facades\Gate;
10 
11class PostController extends Controller
12{
13    /**
14     * Update the given post.
15     */
16    public function update(Request $request, Post $post): RedirectResponse
17    {
18        if (! Gate::allows('update-post', $post)) {
19            abort(403);
20        }
21 
22        // Update the post...
23 
24        return redirect('/posts');
25    }
26}

如果想判斷除了目前登入使用者以外其他的使用者能否執行特定動作，可以使用 Gate Facade 上的 forUser 方法：

1if (Gate::forUser($user)->allows('update-post', $post)) {
2    // The user can update the post...
3}
4 
5if (Gate::forUser($user)->denies('update-post', $post)) {
6    // The user can't update the post...
7}
1if (Gate::forUser($user)->allows('update-post', $post)) {
2    // The user can update the post...
3}
4 
5if (Gate::forUser($user)->denies('update-post', $post)) {
6    // The user can't update the post...
7}

可以通過 any 或 none 方法來在任何時候授權多個動作：

1if (Gate::any(['update-post', 'delete-post'], $post)) {
2    // The user can update or delete the post...
3}
4 
5if (Gate::none(['update-post', 'delete-post'], $post)) {
6    // The user can't update or delete the post...
7}
1if (Gate::any(['update-post', 'delete-post'], $post)) {
2    // The user can update or delete the post...
3}
4 
5if (Gate::none(['update-post', 'delete-post'], $post)) {
6    // The user can't update or delete the post...
7}

Authorizing or Throwing Exceptions

If you would like to attempt to authorize an action and automatically throw an Illuminate\Auth\Access\AuthorizationException if the user is not allowed to perform the given action, you may use the Gate facade's authorize method. Instances of AuthorizationException are automatically converted to a 403 HTTP response by Laravel:

1Gate::authorize('update-post', $post);
2 
3// The action is authorized...
1Gate::authorize('update-post', $post);
2 
3// The action is authorized...

提供額外的上下文

用於授權權限的 Gate 方法 (allows, denies, check, any, none, authorize, can, cannot) 與授權的 Blade 指示詞 (@can, @cannot, @canany) 都接受一個陣列作為其第二引數。這些陣列的元素會被作為引數傳給 Gate 閉包，並且可在進行權限認證時提供額外的上下文：

 1use App\Models\Category;
 2use App\Models\User;
 3use Illuminate\Support\Facades\Gate;
 4 
 5Gate::define('create-post', function (User $user, Category $category, bool $pinned) {
 6    if (! $user->canPublishToGroup($category->group)) {
 7        return false;
 8    } elseif ($pinned && ! $user->canPinPosts()) {
 9        return false;
10    }
11 
12    return true;
13});
14 
15if (Gate::check('create-post', [$category, $pinned])) {
16    // The user can create the post...
17}
 1use App\Models\Category;
 2use App\Models\User;
 3use Illuminate\Support\Facades\Gate;
 4 
 5Gate::define('create-post', function (User $user, Category $category, bool $pinned) {
 6    if (! $user->canPublishToGroup($category->group)) {
 7        return false;
 8    } elseif ($pinned && ! $user->canPinPosts()) {
 9        return false;
10    }
11 
12    return true;
13});
14 
15if (Gate::check('create-post', [$category, $pinned])) {
16    // The user can create the post...
17}

Gate 回應

到目前為止，我們只看過了回傳簡單布林值的 Gate。但，有時候我們可能會想回傳一些更具體的回覆，並在其中包含錯誤訊息。為此，可以在 Gate 內回傳 Illuminate\Auth\Access\Response：

1use App\Models\User;
2use Illuminate\Auth\Access\Response;
3use Illuminate\Support\Facades\Gate;
4 
5Gate::define('edit-settings', function (User $user) {
6    return $user->isAdmin
7                ? Response::allow()
8                : Response::deny('You must be an administrator.');
9});
1use App\Models\User;
2use Illuminate\Auth\Access\Response;
3use Illuminate\Support\Facades\Gate;
4 
5Gate::define('edit-settings', function (User $user) {
6    return $user->isAdmin
7                ? Response::allow()
8                : Response::deny('You must be an administrator.');
9});

即使從 Gate 內回傳授權回應，Gate::allows 方法依然會回傳簡單的布林值。不過，可以使用 Gate::inspect 方法來取得 Gate 回傳的完整授權回應：

1$response = Gate::inspect('edit-settings');
2 
3if ($response->allowed()) {
4    // The action is authorized...
5} else {
6    echo $response->message();
7}
1$response = Gate::inspect('edit-settings');
2 
3if ($response->allowed()) {
4    // The action is authorized...
5} else {
6    echo $response->message();
7}

在使用 Gate::authorize 方法時，若動作未被授權，會回傳 AuthorizationException。這時，授權回應所提供的錯誤訊息會進一步被傳給 HTTP 回應：

1Gate::authorize('edit-settings');
2 
3// The action is authorized...
1Gate::authorize('edit-settings');
2 
3// The action is authorized...

自定 HTTP Response 狀態

當 Gate 拒絕某個動作時，會回傳 403 HTTP Response。不過，在某些情況下，若能回傳其他的 HTTP 狀態碼更好。我們可以使用 Illuminate\Auth\Access\Response 類別的 denyWithStatus 靜態建構函式來自訂在授權檢查失敗的時候要回傳的 HTTP 狀態碼：

1use App\Models\User;
2use Illuminate\Auth\Access\Response;
3use Illuminate\Support\Facades\Gate;
4 
5Gate::define('edit-settings', function (User $user) {
6    return $user->isAdmin
7                ? Response::allow()
8                : Response::denyWithStatus(404);
9});
1use App\Models\User;
2use Illuminate\Auth\Access\Response;
3use Illuminate\Support\Facades\Gate;
4 
5Gate::define('edit-settings', function (User $user) {
6    return $user->isAdmin
7                ? Response::allow()
8                : Response::denyWithStatus(404);
9});

而因為使用 404 Response 來隱藏資源是在 Web App 中常見的手段，因此為了方便， Laravel 也提供了 denyAsNotFound 方法：

1use App\Models\User;
2use Illuminate\Auth\Access\Response;
3use Illuminate\Support\Facades\Gate;
4 
5Gate::define('edit-settings', function (User $user) {
6    return $user->isAdmin
7                ? Response::allow()
8                : Response::denyAsNotFound();
9});
1use App\Models\User;
2use Illuminate\Auth\Access\Response;
3use Illuminate\Support\Facades\Gate;
4 
5Gate::define('edit-settings', function (User $user) {
6    return $user->isAdmin
7                ? Response::allow()
8                : Response::denyAsNotFound();
9});

攔截 Gate 檢查

有的時候，我們可能會想授權特定使用者所有的權限。可以使用 before 方法來定義會在所有權限檢查前執行的閉包：

1use App\Models\User;
2use Illuminate\Support\Facades\Gate;
3 
4Gate::before(function (User $user, string $ability) {
5    if ($user->isAdministrator()) {
6        return true;
7    }
8});
1use App\Models\User;
2use Illuminate\Support\Facades\Gate;
3 
4Gate::before(function (User $user, string $ability) {
5    if ($user->isAdministrator()) {
6        return true;
7    }
8});

若 before 閉包回傳了一個非 null 的結果，則該結果值會被當作權限檢查的結果。

可以使用 after 方法來定義一個會在所有其他權限檢查後執行的閉包：

1use App\Models\User;
2 
3Gate::after(function (User $user, string $ability, bool|null $result, mixed $arguments) {
4    if ($user->isAdministrator()) {
5        return true;
6    }
7});
1use App\Models\User;
2 
3Gate::after(function (User $user, string $ability, bool|null $result, mixed $arguments) {
4    if ($user->isAdministrator()) {
5        return true;
6    }
7});

與 before 方法類似，若 after 閉包回傳了非 null 的結果，則該結果會被當作權限檢查的結果。

內嵌授權

Occasionally, you may wish to determine if the currently authenticated user is authorized to perform a given action without writing a dedicated gate that corresponds to the action. Laravel allows you to perform these types of "inline" authorization checks via the Gate::allowIf and Gate::denyIf methods. Inline authorization does not execute any defined "before" or "after" authorization hooks:

1use App\Models\User;
2use Illuminate\Support\Facades\Gate;
3 
4Gate::allowIf(fn (User $user) => $user->isAdministrator());
5 
6Gate::denyIf(fn (User $user) => $user->banned());
1use App\Models\User;
2use Illuminate\Support\Facades\Gate;
3 
4Gate::allowIf(fn (User $user) => $user->isAdministrator());
5 
6Gate::denyIf(fn (User $user) => $user->banned());

若該動作未授權、或是使用者未登入，則 Laravel 會自動擲回 Illuminate\Auth\Access\AuthorizationException 例外。AuthorizationException 實體會自動由 Laravel 的例外處理常式轉換為 403 HTTP 回應。

建立 Policy

產生 Policy

Policy 是用來依照特定 Model 或資源阻止授權邏輯的類別。舉例來說，若你的專案是個部落格，則可能會有 App\Models\Post Model 以及對應的 App\Policies\PostPolicy 來授權使用者進行建立或更新貼文之類的動作。

可以通過 make:policy Artisan 指令來產生 Policy。產生的 Policy 會被放在 app/Policies 目錄內。若專案中沒有該目錄中，則 Laravel 會自動建立：

1php artisan make:policy PostPolicy
1php artisan make:policy PostPolicy

make:policy 指令會產生一個空的 Policy 類別。若想產生一個與檢視 (View)、建立 (Create)、更新 (Update)、刪除 (Delete) 資源有關的範例 方法的 Policy 類別，可以在執行指令時提供 --model 選項：

1php artisan make:policy PostPolicy --model=Post
1php artisan make:policy PostPolicy --model=Post

註冊 Policy

Policy Discovery

By default, Laravel automatically discover policies as long as the model and policy follow standard Laravel naming conventions. Specifically, the policies must be in a Policies directory at or above the directory that contains your models. So, for example, the models may be placed in the app/Models directory while the policies may be placed in the app/Policies directory. In this situation, Laravel will check for policies in app/Models/Policies then app/Policies. In addition, the policy name must match the model name and have a Policy suffix. So, a User model would correspond to a UserPolicy policy class.

If you would like to define your own policy discovery logic, you may register a custom policy discovery callback using the Gate::guessPolicyNamesUsing method. Typically, this method should be called from the boot method of your application's AppServiceProvider:

1use Illuminate\Support\Facades\Gate;
2 
3Gate::guessPolicyNamesUsing(function (string $modelClass) {
4    // Return the name of the policy class for the given model...
5});
1use Illuminate\Support\Facades\Gate;
2 
3Gate::guessPolicyNamesUsing(function (string $modelClass) {
4    // Return the name of the policy class for the given model...
5});

Manually Registering Policies

Using the Gate facade, you may manually register policies and their corresponding models within the boot method of your application's AppServiceProvider:

 1use App\Models\Order;
 2use App\Policies\OrderPolicy;
 3use Illuminate\Support\Facades\Gate;
 4 
 5/**
 6 * Bootstrap any application services.
 7 */
 8public function boot(): void
 9{
10    Gate::policy(Order::class, OrderPolicy::class);
11}
 1use App\Models\Order;
 2use App\Policies\OrderPolicy;
 3use Illuminate\Support\Facades\Gate;
 4 
 5/**
 6 * Bootstrap any application services.
 7 */
 8public function boot(): void
 9{
10    Gate::policy(Order::class, OrderPolicy::class);
11}

撰寫 Policy

Policy 方法

註冊好 Policy 類別後，可以為每個授權的動作加上方法。舉例來說，我們來在 PostPolicy 中定義一個 update 方法，用來判斷給定的 App\Models\User 可否更新給定的 App\Models\Post 實體。

update 方法會在其引數內收到 User 與 Post 實體，並且應回傳 true 或 false 來判斷該使用者是否有權限更新給定的 Post。因此，在這個例子中，我們會認證使用者的 id 是否與貼文的 user_id 相符：

 1<?php
 2 
 3namespace App\Policies;
 4 
 5use App\Models\Post;
 6use App\Models\User;
 7 
 8class PostPolicy
 9{
10    /**
11     * Determine if the given post can be updated by the user.
12     */
13    public function update(User $user, Post $post): bool
14    {
15        return $user->id === $post->user_id;
16    }
17}
 1<?php
 2 
 3namespace App\Policies;
 4 
 5use App\Models\Post;
 6use App\Models\User;
 7 
 8class PostPolicy
 9{
10    /**
11     * Determine if the given post can be updated by the user.
12     */
13    public function update(User $user, Post $post): bool
14    {
15        return $user->id === $post->user_id;
16    }
17}

我們可以繼續在 Policy 內為各種所需的權限檢查定義更多額外方法。舉例來說，我們可以定義 view 或 delete 方法來對各種與 Post 有關的動作進行權限檢查。但不要忘了，你可以隨意為 Policy 的方法命名。

通過 Artisan 主控台產生 Policy 時若有使用 --model 選項，則 Policy 就已經包含了 viewAny, view, create, update, delete, restore 與 forceDelete 動作的方法。

Policy 回應

到目前為止，我們只看過了回傳簡單布林值的 Policy 方法。但，有時候我們可能會想回傳一些更具體的回覆，並在其中包含錯誤訊息。為此，可以在 Policy 方法內回傳 Illuminate\Auth\Access\Response：

 1use App\Models\Post;
 2use App\Models\User;
 3use Illuminate\Auth\Access\Response;
 4 
 5/**
 6 * Determine if the given post can be updated by the user.
 7 */
 8public function update(User $user, Post $post): Response
 9{
10    return $user->id === $post->user_id
11                ? Response::allow()
12                : Response::deny('You do not own this post.');
13}
 1use App\Models\Post;
 2use App\Models\User;
 3use Illuminate\Auth\Access\Response;
 4 
 5/**
 6 * Determine if the given post can be updated by the user.
 7 */
 8public function update(User $user, Post $post): Response
 9{
10    return $user->id === $post->user_id
11                ? Response::allow()
12                : Response::deny('You do not own this post.');
13}

當從 Policy 內回傳授權回應時，Gate::allows 方法依然會回傳簡單的布林值。不過，可以使用 Gate::inspect 方法來取得 Gate 回傳的完整授權回應：

1use Illuminate\Support\Facades\Gate;
2 
3$response = Gate::inspect('update', $post);
4 
5if ($response->allowed()) {
6    // The action is authorized...
7} else {
8    echo $response->message();
9}
1use Illuminate\Support\Facades\Gate;
2 
3$response = Gate::inspect('update', $post);
4 
5if ($response->allowed()) {
6    // The action is authorized...
7} else {
8    echo $response->message();
9}

在使用 Gate::authorize 方法時，若動作未被授權，會回傳 AuthorizationException。這時，授權回應所提供的錯誤訊息會進一步被傳給 HTTP 回應：

1Gate::authorize('update', $post);
2 
3// The action is authorized...
1Gate::authorize('update', $post);
2 
3// The action is authorized...

Customizing the HTTP Response Status

當 Policy 方法拒絕某個動作時，會回傳 403 HTTP Response。不過，在某些情況下，若能回傳其他的 HTTP 狀態碼更好。我們可以使用 Illuminate\Auth\Access\Response 類別的 denyWithStatus 靜態建構函式來自訂在授權檢查失敗的時候要回傳的 HTTP 狀態碼：

 1use App\Models\Post;
 2use App\Models\User;
 3use Illuminate\Auth\Access\Response;
 4 
 5/**
 6 * Determine if the given post can be updated by the user.
 7 */
 8public function update(User $user, Post $post): Response
 9{
10    return $user->id === $post->user_id
11                ? Response::allow()
12                : Response::denyWithStatus(404);
13}
 1use App\Models\Post;
 2use App\Models\User;
 3use Illuminate\Auth\Access\Response;
 4 
 5/**
 6 * Determine if the given post can be updated by the user.
 7 */
 8public function update(User $user, Post $post): Response
 9{
10    return $user->id === $post->user_id
11                ? Response::allow()
12                : Response::denyWithStatus(404);
13}

而因為使用 404 Response 來隱藏資源是在 Web App 中常見的手段，因此為了方便， Laravel 也提供了 denyAsNotFound 方法：

 1use App\Models\Post;
 2use App\Models\User;
 3use Illuminate\Auth\Access\Response;
 4 
 5/**
 6 * Determine if the given post can be updated by the user.
 7 */
 8public function update(User $user, Post $post): Response
 9{
10    return $user->id === $post->user_id
11                ? Response::allow()
12                : Response::denyAsNotFound();
13}
 1use App\Models\Post;
 2use App\Models\User;
 3use Illuminate\Auth\Access\Response;
 4 
 5/**
 6 * Determine if the given post can be updated by the user.
 7 */
 8public function update(User $user, Post $post): Response
 9{
10    return $user->id === $post->user_id
11                ? Response::allow()
12                : Response::denyAsNotFound();
13}

沒有 Model 的方法

有些 Policy 方法只會收到目前登入使用者的實體。最常見的情況就是在授權 create 動作時。舉例來說，若正在建立部落格，則可能會想判斷某個使用者是否有權限建立任何貼文。在這種情況想，Policy 方法應該只會收到使用者實體：

1/**
2 * Determine if the given user can create posts.
3 */
4public function create(User $user): bool
5{
6    return $user->role == 'writer';
7}
1/**
2 * Determine if the given user can create posts.
3 */
4public function create(User $user): bool
5{
6    return $user->role == 'writer';
7}

訪客使用者

預設情況下，當連入 HTTP 請求並不是由已登入使用者發起的時候，所有的 Gate 與 Policy 都會回傳 false。不過，我們可以通過在使用者的引數定義上定義「可選」的型別提示，或是提供一個 null 預設值，來讓這些權限檢查可以進到 Gate 與 Policy 中：

 1<?php
 2 
 3namespace App\Policies;
 4 
 5use App\Models\Post;
 6use App\Models\User;
 7 
 8class PostPolicy
 9{
10    /**
11     * Determine if the given post can be updated by the user.
12     */
13    public function update(?User $user, Post $post): bool
14    {
15        return $user?->id === $post->user_id;
16    }
17}
 1<?php
 2 
 3namespace App\Policies;
 4 
 5use App\Models\Post;
 6use App\Models\User;
 7 
 8class PostPolicy
 9{
10    /**
11     * Determine if the given post can be updated by the user.
12     */
13    public function update(?User $user, Post $post): bool
14    {
15        return $user?->id === $post->user_id;
16    }
17}

Policy 篩選器

我們可能會想讓特定使用者擁有某個 Policy 中擁有的所有權限。為此，可以在 Policy 內定義一個 before 方法。before 方法會在 Policy 內任何其他方法之前被執行，如此一來我們便有機會可以在預定的 Policy 方法被實際執行前對該行為進行授權。這個功能最常見的使用情況就是用來授權網站管理員來進行所有動作：

 1use App\Models\User;
 2 
 3/**
 4 * Perform pre-authorization checks.
 5 */
 6public function before(User $user, string $ability): bool|null
 7{
 8    if ($user->isAdministrator()) {
 9        return true;
10    }
11 
12    return null;
13}
 1use App\Models\User;
 2 
 3/**
 4 * Perform pre-authorization checks.
 5 */
 6public function before(User $user, string $ability): bool|null
 7{
 8    if ($user->isAdministrator()) {
 9        return true;
10    }
11 
12    return null;
13}

若拒絕特定類型的使用者的所有授權，可以在 before 方法內回傳 false。若回傳 null，則權限檢查會繼續傳到 Policy 方法內。

通過 Policy 來授權動作

Via the User Model

Laravel 專案內建的 App\Models\User Model 中包含了兩個實用的方法，可以用來進行權限檢查：can 與 cannot。can 與 cannot 方法接收用要進行權限檢查的動作名稱，以及相關的 Model。舉例來說，讓我們來判斷某個使用者是否有權限更新給定的 App\Models\Post Model。一般來說，這個檢查會在 Controller 的方法內進行：

 1<?php
 2 
 3namespace App\Http\Controllers;
 4 
 5use App\Http\Controllers\Controller;
 6use App\Models\Post;
 7use Illuminate\Http\RedirectResponse;
 8use Illuminate\Http\Request;
 9 
10class PostController extends Controller
11{
12    /**
13     * Update the given post.
14     */
15    public function update(Request $request, Post $post): RedirectResponse
16    {
17        if ($request->user()->cannot('update', $post)) {
18            abort(403);
19        }
20 
21        // Update the post...
22 
23        return redirect('/posts');
24    }
25}
 1<?php
 2 
 3namespace App\Http\Controllers;
 4 
 5use App\Http\Controllers\Controller;
 6use App\Models\Post;
 7use Illuminate\Http\RedirectResponse;
 8use Illuminate\Http\Request;
 9 
10class PostController extends Controller
11{
12    /**
13     * Update the given post.
14     */
15    public function update(Request $request, Post $post): RedirectResponse
16    {
17        if ($request->user()->cannot('update', $post)) {
18            abort(403);
19        }
20 
21        // Update the post...
22 
23        return redirect('/posts');
24    }
25}

若已為給定的 Model 註冊好 Policy，則 can 方法會自動呼叫適當的 Policy，並回傳布林結果值。若沒有為該 Model 註冊好的 Policy，則 can 方法會呼叫符合給定動作名稱的閉包 Gate。

不需要 Model 的動作

請記得，某些對應到 Policy 方法的動作，如 create，並不要求 Model 實體。這種情況下，可以將類別名稱傳給 can 方法。類別名稱會用來判斷對動作進行權限檢查時要使用哪個 Policy：

 1<?php
 2 
 3namespace App\Http\Controllers;
 4 
 5use App\Http\Controllers\Controller;
 6use App\Models\Post;
 7use Illuminate\Http\RedirectResponse;
 8use Illuminate\Http\Request;
 9 
10class PostController extends Controller
11{
12    /**
13     * Create a post.
14     */
15    public function store(Request $request): RedirectResponse
16    {
17        if ($request->user()->cannot('create', Post::class)) {
18            abort(403);
19        }
20 
21        // Create the post...
22 
23        return redirect('/posts');
24    }
25}
 1<?php
 2 
 3namespace App\Http\Controllers;
 4 
 5use App\Http\Controllers\Controller;
 6use App\Models\Post;
 7use Illuminate\Http\RedirectResponse;
 8use Illuminate\Http\Request;
 9 
10class PostController extends Controller
11{
12    /**
13     * Create a post.
14     */
15    public function store(Request $request): RedirectResponse
16    {
17        if ($request->user()->cannot('create', Post::class)) {
18            abort(403);
19        }
20 
21        // Create the post...
22 
23        return redirect('/posts');
24    }
25}

Via the Gate Facade

In addition to helpful methods provided to the App\Models\User model, you can always authorize actions via the Gate facade's authorize method.

與 can 方法類似，這個方法接收要進行權限檢查的動作名稱、以及相關的 Model。若該動作未被授權，則 authorize 方法會擲回 Illuminate\Auth\Access\AuthroizationException 例外，Laravel 的例外處理常式會自動將該例外轉成有 403 狀態碼的 HTTP 回應：

 1<?php
 2 
 3namespace App\Http\Controllers;
 4 
 5use App\Http\Controllers\Controller;
 6use App\Models\Post;
 7use Illuminate\Http\RedirectResponse;
 8use Illuminate\Http\Request;
 9use Illuminate\Support\Facades\Gate;
10 
11class PostController extends Controller
12{
13    /**
14     * Update the given blog post.
15     *
16     * @throws \Illuminate\Auth\Access\AuthorizationException
17     */
18    public function update(Request $request, Post $post): RedirectResponse
19    {
20        Gate::authorize('update', $post);
21 
22        // The current user can update the blog post...
23 
24        return redirect('/posts');
25    }
26}
 1<?php
 2 
 3namespace App\Http\Controllers;
 4 
 5use App\Http\Controllers\Controller;
 6use App\Models\Post;
 7use Illuminate\Http\RedirectResponse;
 8use Illuminate\Http\Request;
 9use Illuminate\Support\Facades\Gate;
10 
11class PostController extends Controller
12{
13    /**
14     * Update the given blog post.
15     *
16     * @throws \Illuminate\Auth\Access\AuthorizationException
17     */
18    public function update(Request $request, Post $post): RedirectResponse
19    {
20        Gate::authorize('update', $post);
21 
22        // The current user can update the blog post...
23 
24        return redirect('/posts');
25    }
26}

不需要 Model 的動作

與前面討論過的一樣，某些 Policy 方法，如 create，並不要求 Model 實體。這種情況下，應將類別名稱傳給 authorize 方法。類別名稱會用來判斷對動作進行權限檢查時要使用哪個 Policy：

 1use App\Models\Post;
 2use Illuminate\Http\RedirectResponse;
 3use Illuminate\Http\Request;
 4use Illuminate\Support\Facades\Gate;
 5 
 6/**
 7 * Create a new blog post.
 8 *
 9 * @throws \Illuminate\Auth\Access\AuthorizationException
10 */
11public function create(Request $request): RedirectResponse
12{
13    Gate::authorize('create', Post::class);
14 
15    // The current user can create blog posts...
16 
17    return redirect('/posts');
18}
 1use App\Models\Post;
 2use Illuminate\Http\RedirectResponse;
 3use Illuminate\Http\Request;
 4use Illuminate\Support\Facades\Gate;
 5 
 6/**
 7 * Create a new blog post.
 8 *
 9 * @throws \Illuminate\Auth\Access\AuthorizationException
10 */
11public function create(Request $request): RedirectResponse
12{
13    Gate::authorize('create', Post::class);
14 
15    // The current user can create blog posts...
16 
17    return redirect('/posts');
18}

通過 Middleware

Laravel includes a middleware that can authorize actions before the incoming request even reaches your routes or controllers. By default, the Illuminate\Auth\Middleware\Authorize middleware may be attached to a route using the can middleware alias, which is automatically registered by Laravel. Let's explore an example of using the can middleware to authorize that a user can update a post:

1use App\Models\Post;
2 
3Route::put('/post/{post}', function (Post $post) {
4    // The current user may update the post...
5})->middleware('can:update,post');
1use App\Models\Post;
2 
3Route::put('/post/{post}', function (Post $post) {
4    // The current user may update the post...
5})->middleware('can:update,post');

在此例子中，我們將兩個引數傳給了 can Middleware。第一個引數是我們想進行權限檢查的動作名稱，而第二個引數是我們想傳給 Policy 方法的路由參數。在這個例子中，由於我們使用了隱式 Model 繫結，所以會將 App\Models\Post Model 傳給 Policy 方法。若使用者沒有權限執行給定的動作，則這個 Middleware 會回傳狀態碼 403 的 HTTP 回應。

為了方便起見，也可以使用 can 方法來將 can Middleware 附加到路由上：

1use App\Models\Post;
2 
3Route::put('/post/{post}', function (Post $post) {
4    // The current user may update the post...
5})->can('update', 'post');
1use App\Models\Post;
2 
3Route::put('/post/{post}', function (Post $post) {
4    // The current user may update the post...
5})->can('update', 'post');

不需要 Model 的動作

再強調一次，某些 Policy 方法，如 create，並不要求 Model 實體。這種情況下，可以將類別名稱傳給 Middleware。這個類別名稱會用來判斷對動作進行權限檢查時要使用哪個 Policy：

1Route::post('/post', function () {
2    // The current user may create posts...
3})->middleware('can:create,App\Models\Post');
1Route::post('/post', function () {
2    // The current user may create posts...
3})->middleware('can:create,App\Models\Post');

在字串形式的 Middleware 定義中指定完整的類別名稱可能會有點麻煩。因此，我們也可以使用 can 方法來將 can Middleware 附加到路由上：

1use App\Models\Post;
2 
3Route::post('/post', function () {
4    // The current user may create posts...
5})->can('create', Post::class);
1use App\Models\Post;
2 
3Route::post('/post', function () {
4    // The current user may create posts...
5})->can('create', Post::class);

通過 Blade 樣板

在撰寫 Blade 樣板時，我們可能會在使用者有權限執行給定動作時顯示某一部分的頁面。舉例來說，我們可能想在使用者真的可以更新貼文時才顯示更新表單。這時，可以使用 @can 與 @cannot 指示詞：

 1@can('update', $post)
 2    <!-- The current user can update the post... -->
 3@elsecan('create', App\Models\Post::class)
 4    <!-- The current user can create new posts... -->
 5@else
 6    <!-- ... -->
 7@endcan
 8 
 9@cannot('update', $post)
10    <!-- The current user cannot update the post... -->
11@elsecannot('create', App\Models\Post::class)
12    <!-- The current user cannot create new posts... -->
13@endcannot
 1@can('update', $post)
 2    <!-- The current user can update the post... -->
 3@elsecan('create', App\Models\Post::class)
 4    <!-- The current user can create new posts... -->
 5@else
 6    <!-- ... -->
 7@endcan
 8 
 9@cannot('update', $post)
10    <!-- The current user cannot update the post... -->
11@elsecannot('create', App\Models\Post::class)
12    <!-- The current user cannot create new posts... -->
13@endcannot

這些指示詞是撰寫 @if 與 @unless 陳述式時的方便捷徑。上方的 @can 與 @cannot 陳述式與下列陳述式相同：

1@if (Auth::user()->can('update', $post))
2    <!-- The current user can update the post... -->
3@endif
4 
5@unless (Auth::user()->can('update', $post))
6    <!-- The current user cannot update the post... -->
7@endunless
1@if (Auth::user()->can('update', $post))
2    <!-- The current user can update the post... -->
3@endif
4 
5@unless (Auth::user()->can('update', $post))
6    <!-- The current user cannot update the post... -->
7@endunless

可以在包含一系列動作的陣列中判斷某個使用者是否有權限執行其中的任意動作。為此，請使用 @canany 指示詞：

1@canany(['update', 'view', 'delete'], $post)
2    <!-- The current user can update, view, or delete the post... -->
3@elsecanany(['create'], \App\Models\Post::class)
4    <!-- The current user can create a post... -->
5@endcanany
1@canany(['update', 'view', 'delete'], $post)
2    <!-- The current user can update, view, or delete the post... -->
3@elsecanany(['create'], \App\Models\Post::class)
4    <!-- The current user can create a post... -->
5@endcanany

不需要 Model 的動作

與其他大多數的授權方法一樣，當某個動作不需要 Model 實體時，可以將類別名稱傳給 @can 與 @cannot 指示詞：

1@can('create', App\Models\Post::class)
2    <!-- The current user can create posts... -->
3@endcan
4 
5@cannot('create', App\Models\Post::class)
6    <!-- The current user can't create posts... -->
7@endcannot
1@can('create', App\Models\Post::class)
2    <!-- The current user can create posts... -->
3@endcan
4 
5@cannot('create', App\Models\Post::class)
6    <!-- The current user can't create posts... -->
7@endcannot

提供額外的上下文

當使用 Policy 對動作進行權限檢查時，可以將陣列作為第二引數傳給各種權限檢查函式與輔助函式。陣列中的第一個元素是用來判斷要叫用哪個 Policy 的，而剩下的元素則會作為參數傳給 Policy 方法，可用來在做權限檢查時提供額外的上下文。舉例來說，假設有下列 PostPolicy 方法定義，其中包含了一個額外的 $category 參數：

1/**
2 * Determine if the given post can be updated by the user.
3 */
4public function update(User $user, Post $post, int $category): bool
5{
6    return $user->id === $post->user_id &&
7           $user->canUpdateCategory($category);
8}
1/**
2 * Determine if the given post can be updated by the user.
3 */
4public function update(User $user, Post $post, int $category): bool
5{
6    return $user->id === $post->user_id &&
7           $user->canUpdateCategory($category);
8}

在嘗試判斷登入使用者能否更新給定貼文時，我們可以像這樣叫用該 Policy 方法：

 1/**
 2 * Update the given blog post.
 3 *
 4 * @throws \Illuminate\Auth\Access\AuthorizationException
 5 */
 6public function update(Request $request, Post $post): RedirectResponse
 7{
 8    Gate::authorize('update', [$post, $request->category]);
 9 
10    // The current user can update the blog post...
11 
12    return redirect('/posts');
13}
 1/**
 2 * Update the given blog post.
 3 *
 4 * @throws \Illuminate\Auth\Access\AuthorizationException
 5 */
 6public function update(Request $request, Post $post): RedirectResponse
 7{
 8    Gate::authorize('update', [$post, $request->category]);
 9 
10    // The current user can update the blog post...
11 
12    return redirect('/posts');
13}