Closure::bindTo

(PHP 5 >= 5.4.0)

Closure::bindTo — 复制当前闭包对象，绑定指定的$this对象和类作用域。

说明

public Closure Closure::bindTo ( object $newthis [, mixed $newscope = 'static' ] )

创建并返回一个匿名函数，它与当前对象的函数体相同、绑定了同样变量，但可以绑定不同的对象，也可以绑定新的类作用域。

“绑定的对象”决定了函数体中的 $this 的取值，“类作用域”代表一个类型、决定在这个匿名函数中能够调用哪些私有和保护的方法。也就是说，此时 $this 可以调用的方法，与 newscope 类的成员函数是相同的。

静态闭包不能有绑定的对象（ newthis 参数的值应该设为 NULL ）不过仍然可以用 bubdTo 方法来改变它们的类作用域。

This function will ensure that for a non-static closure, having a bound instance will imply being scoped and vice-versa. To this end, non-static closures that are given a scope but a NULL instance are made static and non-static non-scoped closures that are given a non-null instance are scoped to an unspecified class.

Note:

如果你只是想要复制一个匿名函数，可以用 cloning 代替。

参数

newthis: 绑定给匿名函数的一个对象，或者 NULL 来取消绑定。
newscope: 关联到匿名函数的类作用域，或者 'static' 保持当前状态。如果是一个对象，则使用这个对象的类型为心得类作用域。这会决定绑定的对象的保护、私有成员方法的可见性。

返回值

返回新创建的 Closure 对象或者在失败时返回 FALSE

范例

Example #1 Closure::bindTo() 实例

  <?php

 class  A  {
    function  __construct ( $val ) {
         $this -> val  =  $val ;
    }
    function  getClosure () {
         //returns closure bound to this object and scope
         return function() { return  $this -> val ; };
    }
}

 $ob1  = new  A ( 1 );
 $ob2  = new  A ( 2 );

 $cl  =  $ob1 -> getClosure ();
echo  $cl (),  "\n" ;
 $cl  =  $cl -> bindTo ( $ob2 );
echo  $cl (),  "\n" ;
 ?>

以上例程的输出类似于：

1
2

参见

匿名函数
Closure::bind() - 复制一个闭包，绑定指定的$this对象和类作用域。

用户评论:

[#1] Nezar Fadle [2015-01-19 10:40:04]

We can use the concept of bindTo to write a very small Template Engine:

#############
index.php
############

<?php class Article{ private $title = "This is an article"; } class Post{ private $title = "This is a post"; } class Template{ function render($context, $tpl){ $closure = function($tpl){ ob_start(); include $tpl; return ob_end_flush(); }; $closure = $closure->bindTo($context, $context); $closure($tpl); } } $art = new Article(); $post = new Post(); $template = new Template(); $template->render($art, 'tpl.php'); $template->render($post, 'tpl.php'); ?>

#############
tpl.php
############
<h1><?php echo $this->title;?></h1>

[#2] tatarynowicz at gmail dot com [2013-02-14 09:30:38]

You can do pretty Javascript-like things with objects using closure binding:

<?php trait DynamicDefinition { public function __call($name, $args) { if (is_callable($this->$name)) { return call_user_func($this->$name, $args); } else { throw new \RuntimeException("Method {$name} does not exist"); } } public function __set($name, $value) { $this->$name = is_callable($value)? $value->bindTo($this, $this): $value; } } class Foo { use DynamicDefinition; private $privateValue = 'I am private'; } $foo = new Foo; $foo->bar = function() { return $this->privateValue; }; // prints 'I am private' print $foo->bar(); ?>

[#3] safakozpinar at gmail dot com [2012-03-09 13:35:02]

Private/protected members are accessible if you set the "newscope" argument (as the manual says).

<?php
$fn = function(){
    return ++$this->foo; // increase the value
};

class Bar{
    private $foo = 1; // initial value
}

$bar = new Bar();

$fn1 = $fn->bindTo($bar, 'Bar'); // specify class name
$fn2 = $fn->bindTo($bar,  $bar); // or object

echo $fn1(); // 2
echo $fn2(); // 3

[#4] anthony bishopric [2012-03-03 01:00:43]

Closures can rebind their $this variable, but private/protected methods and functions of $this are not accessible to the closures.

<?php
$fn = function(){
return $this->foo;
};

class Bar{
private $foo = 3;
}

$bar = new Bar();

$fn = $fn->bindTo($bar);

echo $fn(); // Fatal error: Cannot access private property Bar::$foo

[#5] amica at php-resource dot de [2011-12-18 16:23:48]

With rebindable $this at hand it's possible to do evil stuff:

<?php class A { private $a = 12; private function getA () { return $this->a; } } class B { private $b = 34; private function getB () { return $this->b; } } $a = new A(); $b = new B(); $c = function () { if (property_exists($this, "a") && method_exists($this, "getA")) { $this->a++; return $this->getA(); } if (property_exists($this, "b") && method_exists($this, "getB")) { $this->b++; return $this->getB(); } }; $ca = $c->bindTo($a, $a); $cb = $c->bindTo($b, $b); echo $ca(), "\n"; // => 13 echo $cb(), "\n"; // => 35 ?>