从类中定义一个闭包作为方法 [英] define a closure as method from class

问题描述

我试图使用php5.3和闭包。

我看到这里（清单7.关闭一个对象： http://www.ibm.com/developerworks/opensource/library/os- php-5.3new2 / index.html ），可以在回调函数中使用$ this，但不是。所以我尝试给$作为使用变量：

  $ self = $ this; 
 $ foo = function（）use（$ self）{//使用$ self做某事} 
  

所以使用同样的例子：

  class Dog 
 {
 private $ _name; 
 protected $ _color; 
 
 public function __construct（$ name，$ color）
 {
 $ this-> _name = $ name; 
 $ this-> _color = $ color; 
} 
 public function greet（$ greeting）
 {
 $ self = $ this; 
 return function（）use（$ greeting，$ self）{
 echo$ greeting，I am a {$ self-> _color} dog named {$ self-> _name}。 
}; 
} 
} 
 
 $ dog = new Dog（Rover，red）; 
 $ dog-> greet（Hello）; 
 
输出：
你好，我是一只名叫Rover的红狗。 
  

首先这个例子不打印字符串但返回函数，但这不是我的问题。

其次，我无法访问private或protected，因为回调函数是一个全局函数，而不是来自Dog对象的上下文。这是我的问题。它是相同的：

 函数greet（$ greeting，$ object）{
 echo$ greeting，I am一个名为{$ self-> _name}的{$ self-> _color}狗。 
} 
  

我想要：

  public function greet（$ greeting）{
 echo$ greeting，I are a {$ self-> _color} dog named {$ self-> _name} 。; 
} 
  

这是来自Dog而不是全球。

那么，你不能使用$ this的全部原因是因为闭包是一个背景中的对象（Closure类）。

有两种方法。首先，添加__invoke方法（如果你调用$ obj（）调用方法）。

  class Dog {
 
 public function __invoke（$ method）{
 $ args = func_get_args（）; 
 array_shift（$ args）; //删除方法名
 if（is_callable（array（$ this，$ method）））{
 return call_user_func_array（array（$ this，$ method），$ args）; 
} else {
 throw new BadMethodCallException（'Unknown method：'。$ method）; 
} 
} 
 
 public function greet（$ greeting）{
 $ self = $ this; 
 return function（）use（$ greeting，$ self）{
 $ self（'do_greet'，$ greeting）; 
}; 
} 
 
 protected function do_greet（$ greeting）{
 echo$ greeting，I is a {$ this-> _color} dog named {$ this-> _name }。 
} 
} 
  

如果您希望如果修改主机对象，你可以只改变返回函数为：

  public function greet（$ greeting）{
 $ self =（clone）$ this; 
 return function（）use（$ greeting，$ self）{
 $ self（'do_greet'，$ greeting）; 
}; 
} 
  

另一个选项是提供一个通用的getter：

  class Dog {
 
 public function __get（$ name）{
 return isset（$ this-> $ name）？ $ this-> $ name：null; 
} 
 
} 
  

有关详细信息， a href =http://www.php.net/manual/en/language.oop5.magic.php =nofollow noreferrer> http://www.php.net/manual/en/language.oop5 .magic.php

i'm trying to play with php5.3 and closure.

I see here (Listing 7. Closure inside an object : http://www.ibm.com/developerworks/opensource/library/os-php-5.3new2/index.html) that it's possible to use $this in the callback function, but it's not. So I try to give $this as use variable :

$self = $this;
$foo = function() use($self) { //do something with $self }

So to use the same example :

class Dog
{
private $_name;
protected $_color;

public function __construct($name, $color)
{
     $this->_name = $name;
     $this->_color = $color;
}
public function greet($greeting)
{
     $self = $this;
     return function() use ($greeting, $self) {
         echo "$greeting, I am a {$self->_color} dog named {$self->_name}.";
     };
}
}

$dog = new Dog("Rover","red");
$dog->greet("Hello");

Output:
Hello, I am a red dog named Rover.

First of all this example does not print the string but return the function, but that's not my problem.

Secondly I can't access to private or protected, because the callback function is a global function and not in the context from the Dog object. Tha't my problem. It's the same as :

function greet($greeting, $object) {
    echo "$greeting, I am a {$self->_color} dog named {$self->_name}.";
}

And I want :

public function greet($greeting) {
    echo "$greeting, I am a {$self->_color} dog named {$self->_name}.";
}

Which is from Dog and not global.

解决方案

Well, the whole reason that you can't use $this, is because the closure is an object in the background (the Closure class).

There are two ways around this. First, is add the __invoke method (What's called if you call $obj())..

class Dog {

    public function __invoke($method) {
        $args = func_get_args();
        array_shift($args); //get rid of the method name
        if (is_callable(array($this, $method))) {
            return call_user_func_array(array($this, $method), $args);
        } else {
            throw new BadMethodCallException('Unknown method: '.$method);
        }
    }

    public function greet($greeting) {
        $self = $this;
        return function() use ($greeting, $self) {
            $self('do_greet', $greeting);
        };
    }

    protected function do_greet($greeting) {
        echo "$greeting, I am a {$this->_color} dog named {$this->_name}.";
    }
}

If you want the closure to not change if you modify the host object, you can just change the return function to something like:

public function greet($greeting) {
    $self = (clone) $this;
    return function() use ($greeting, $self) {
        $self('do_greet', $greeting);
    };
}

The other option, is to provide a generic getter:

class Dog {

    public function __get($name) {
        return isset($this->$name) ? $this->$name : null;
    }

}

For more information, see: http://www.php.net/manual/en/language.oop5.magic.php

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