Question

我正在尝试从闭包中引用对象的私有变量。下面的代码似乎有效，但它会抱怨Fatal error: Cannot access self:: when no class scope is active in test.php on line 12和Fatal error: Using $this when not in object context in test.php on line 20。

任何想法如何使用闭包来完成相同的结果，同时保持变量私有而不做辅助函数（打败私有变量的整个想法）。

class MyClass
{

    static private $_var1;
    private $_var2;

    static function setVar1( $value )
    {
        $closure = function () use ( $value ) {
            self::$_var1 = $value;
        };
        $closure();
    }

    function setVar2( $value )
    {
        $closure = function () use ( $value ) {
            $this->_var2 = $value;
        };
        $closure();
    }

}

MyClass::setVar1( "hello" ); //doesn't work

$myclass = new MyClass;
$myclass->setVar2( "hello" ); //doesn't work

Answer 1

编辑注意，此答案原本适用于 PHP5.3 及更早版本，现在可能。有关最新信息，请参阅this answer。

这不是直接可行的。特别是，闭包没有相关的范围，因此他们无法访问私有和受保护的成员。

但是，您可以使用引用：

<?php
class MyClass
{

    static private $_var1;
    private $_var2;

    static function setVar1( $value )
    {
        $field =& self::$_var1;
        $closure = function () use ( $value,  &$field ) {
            $field = $value;
        };
        $closure();
    }

    function setVar2( $value )
    {
        $field =& $this->_var2;
        $closure = function () use ( $value, &$field ) {
            $field = $value;
        };
        $closure();
    }

}

MyClass::setVar1( "hello" );

$myclass = new MyClass;
$myclass->setVar2( "hello" );

Answer 2

这可以从PHP 5.4.0开始

class test {
    function testMe() {
        $test = new test;
        $func = function() use ($test) {
            $test->findMe();        // Can see protected method
            $test::findMeStatically();  // Can see static protected method
        };
        $func();
        return $func;
    }

    protected function findMe() {
        echo " [find Me] \n";
    }

    protected static function findMeStatically() {
        echo " [find Me Statically] \n";
    }
}

$test = new test;
$func = $test->testMe();
$func();        // Can call from another context as long as 
            // the closure was created in the proper context.

Answer 3

闭包没有$this或self的概念 - 它们不以这种方式绑定到对象。这意味着您必须通过use子句传递变量......类似于：

$_var1 =& self::$_var1;
$closure = function() use ($value, &$_var1) {
  $_var1 = $value;
};

$_var2 =& $this->_var2;
$closure = function() use ($value, &$_var2) {
  $_var2 = $value;
};

我没有测试过上面的代码，但我认为这是正确的。

从闭包中访问私有变量

3 个答案: