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
$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
?>