在PHP中动态创建实例方法

问题描述：

我想能够在类的构造函数中动态创建一个实例方法，如下所示：

I'd like to be able to dynamically create an instance method within a class' constructor like so:

class Foo{
   function __construct() {
      $code = 'print hi;';
      $sayHi = create_function( '', $code);
      print "$sayHi"; //prints lambda_2
      print $sayHi(); // prints 'hi'
      $this->sayHi = $sayHi; 
    }
}

$f = new Foo;
$f->sayHi(); //Fatal error: Call to undefined method Foo::sayHi() in /export/home/web/private/htdocs/staff/cohenaa/dev-drupal-2/sites/all/modules/devel/devel.module(1086) : eval()'d code on line 12

问题似乎是lambda_2函数对象在构造函数中没有绑定$ this。

The problem seems to be that the lambda_2 function object is not getting bound to $this within the constructor.

任何帮助都将被欣赏。

答

您将匿名函数分配给属性，但是尝试使用属性名称调用方法。 PHP不能自动从属性中取消引用匿名函数。以下将工作

You are assigning the anonymous function to a property, but then try to call a method with the property name. PHP cannot automatically dereference the anonymous function from the property. The following will work

class Foo{

   function __construct() {
      $this->sayHi = create_function( '', 'print "hi";'); 
    }
}

$foo = new Foo;
$fn = $foo->sayHi;
$fn(); // hi

您可以利用魔术 __调用方法来截取无效的方法调用，以查看是否有一个持有回调/匿名函数的属性：

You can utilize the magic __call method to intercept invalid method calls to see if there is a property holding a callback/anonymous function though:

class Foo{

   public function __construct()
   {
      $this->sayHi = create_function( '', 'print "hi";'); 
   }
   public function __call($method, $args)
   {
       if(property_exists($this, $method)) {
           if(is_callable($this->$method)) {
               return call_user_func_array($this->$method, $args);
           }
       }
   }
}

$foo = new Foo;
$foo->sayHi(); // hi

从PHP5.3开始，您还可以使用

As of PHP5.3, you can also create Lambdas with

$lambda = function() { return TRUE; };

请参阅匿名功能的PHP手册供进一步参考。

在PHP中动态创建实例方法

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