Laravel授权原理讲解第二部分

RequestGuard.php

public function user()
    {
        // If we've already retrieved the user for the current request we can just
        // return it back immediately. We do not want to fetch the user data on
        // every call to this method because that would be tremendously slow.
        if (! is_null($this->user)) {
            return $this->user;
        }

        return $this->user = call_user_func(
            $this->callback, $this->request
        );
    }

接着就是其$this->callback参数：

public function __construct(callable $callback, Request $request)
    {
        $this->request = $request;
        $this->callback = $callback;
    }

然后其实是在AuthManager.php中初始化RequestGuard类：

public function viaRequest($driver, callable $callback)
    {
        return $this->extend($driver, function () use ($callback) {
            $guard = new RequestGuard($callback, $this->app['request']);

            $this->app->refresh('request', $guard, 'setRequest');

            return $guard;
        });
    }

但是线索断了，Laravel中没有调用过该函数，那么我们上面走错了，回到最开始的函数：

if (! is_null($this->user)) {
            return $this->user;
        }

这里的$this->user是怎么设值的呢？这个值来自trait GuardHelpers，那么有没有可能是在别的地方设置过参数呢？不搜不知道，在另外两个文件中都设置过该值：

第一个文件：Illuminate\Auth\SessionGuard.php

第二个文件：Illuminate\Auth\TokenGuard.php

下面分别来看这两个文件，第一个：

    public function user()
    {
        if ($this->loggedOut) {
            return;
        }

        // If we've already retrieved the user for the current request we can just
        // return it back immediately. We do not want to fetch the user data on
        // every call to this method because that would be tremendously slow.
        if (! is_null($this->user)) {
            return $this->user;
        }
        // 这里是从session中获取特定的设置值，假设这里就是获取id
        $id = $this->session->get($this->getName());

        // First we will try to load the user using the identifier in the session if
        // one exists. Otherwise we will check for a "remember me" cookie in this
        // request, and if one exists, attempt to retrieve the user using that.
        $user = null;

        if (! is_null($id)) {
            // 这里是使用数据库驱动从从数据库中获取值
            if ($user = $this->provider->retrieveById($id)) {
                $this->fireAuthenticatedEvent($user);
            }
        }

        // If the user is null, but we decrypt a "recaller" cookie we can attempt to
        // pull the user data on that cookie which serves as a remember cookie on
        // the application. Once we have a user we can return it to the caller.
        $recaller = $this->recaller();

        if (is_null($user) && ! is_null($recaller)) {
            $user = $this->userFromRecaller($recaller);

            if ($user) {
                $this->updateSession($user->getAuthIdentifier());

                $this->fireLoginEvent($user, true);
            }
        }

        return $this->user = $user;
    }

接着就是第二个：

    public function user()
    {
        // If we've already retrieved the user for the current request we can just
        // return it back immediately. We do not want to fetch the user data on
        // every call to this method because that would be tremendously slow.
        if (! is_null($this->user)) {
            return $this->user;
        }

        $user = null;

        $token = $this->getTokenForRequest();

        if (! empty($token)) {
            $user = $this->provider->retrieveByCredentials(
                [$this->storageKey => $token]
            );
        }

        return $this->user = $user;
    }

不用深究这两个函数具体的工作原理，只需要知道这两个函数其实是通过以下途径获取当前用户信息的：

• Cookie
• Session

其中至少有一个保存着当前用户的个人信息，这下回到最开始的Policies下的函数中来：

public function edits(User $currentUser,User $user){
      return $currentUser->id===$user->id;
    }

其中的第一个$currentUser是从Cookie或者Session中获取的值，而第二个参数$user则是我们外部传递进去的函数。虽然不算完美的解释了策略的原理，但是起码找到了突破口了，之后有机会再深入学习吧，现在到此为止了，后面有时间会整理一下，没时间的话，那么只能算了。。。。。。。