問題描述

我在中間看到了一個 Laravel 函數(shù):

I saw one Laravel function in middlewere:

public function handle($request, Closure $next, $guard = null)
{
    if (Auth::guard($guard)->check())
    {
       return redirect('/home');
    } 

    return $next($request);
}

什么是Closure，它有什么作用?

What is Closure and what does it do?

推薦答案

A 關(guān)閉 是一個匿名函數(shù).閉包通常用作回調(diào)方法，并且可以用作函數(shù)中的參數(shù).

A Closure is an anonymous function. Closures are often used as callback methods and can be used as a parameter in a function.

如果你看下面的例子:

function handle(Closure $closure) {
    $closure();
}

handle(function(){
    echo 'Hello!';
});

我們首先在 handle 函數(shù)中添加一個 Closure 參數(shù).這將提示我們 handle 函數(shù)接受一個 Closure.

We start by adding a Closure parameter the handle function. This will type hint us that the handle function takes a Closure.

然后我們調(diào)用 handle 函數(shù)并傳遞一個函數(shù)作為第一個參數(shù).

We then call the handle function and pass a function as the first parameter.

通過在 handle 函數(shù)中使用 $closure(); 我們告訴 PHP 執(zhí)行給定的 Closure 然后 echo'你好！'

By using $closure(); in the handle function we tell PHP to execute the given Closure which will then echo 'Hello!'

也可以將參數(shù)傳遞到 Closure.我們可以通過更改 handle 函數(shù)中的 Closure 調(diào)用來傳遞參數(shù)來實現(xiàn).在這個例子中，我將只傳遞一個字符串，但這可以是任何變量.

It is also possible to pass parameters into a Closure. We can do so by changing the Closure call in the handle function to pass on a parameter. In this example i'll just pass a string but this can be any variable.

handle 函數(shù)現(xiàn)在看起來像

The handle function now looks like

function handle(Closure $closure) {
    $closure('Hello World!');
}

我們現(xiàn)在還需要修改 Closure 本身以獲取參數(shù).我們通過簡單地向函數(shù)添加一個參數(shù)來實現(xiàn).然后我們將該變量傳遞給 echo.

We now also need to modify the Closure itself to take the parameter. We do so by simply adding a parameter to the function. And then we pass that variable to the echo.

函數(shù)現(xiàn)在看起來像

handle(function($value){
    echo $value;
});

哪個將回顯 Hello World!

有關(guān)更多信息，您可以查看以下鏈接:

For more information you can check out these links:

http://php.net/manual/en/functions.anonymous.php

http://php.net/manual/en/class.closure.php

這篇關(guān)于Laravel 中的閉包是什么?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！