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Closure::fromCallable

(PHP 7 >= 7.1.0)

Closure::fromCallableКонвертирует callable в замыкание

Описание

public static Closure Closure::fromCallable ( callable $callable )

Создает и возвращает новую анонимную функцию из заданного callable, используя текущую область видимости. Этот метод проверяет, что callable является типом callable в текущей области видимости и выбрасывает исключение TypeError, если это не так.

Список параметров

callable

Объект типа callable.

Возвращаемые значения

Возвращает новый объект класса Closure или выбрасывает исключение TypeError, если callable не является объектом типа callable в текущей области видимости.

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User Contributed Notes 3 notes

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11
igorchernin at yahoo dot com
1 year ago
It seems that the result of the "fromCallable" behaves a little bit different then an original Lambda function.

class A {
    private $name;
    public function __construct($name)
    {
        $this->name = $name;
    }
}

// test callable
function getName()
{
      return $this->name;
}
$bob = new A("Bob");

$cl1 = Closure::fromCallable("getName");
$cl1 = $cl1->bindTo($bob, 'A');

//This will retrieve: Uncaught Error: Cannot access private property A::$name
$result = $cl1();
echo $result;

//But for a Lambda function
$cl2 = function() {
    return $this->name;
};
$cl2 = $cl2->bindTo($bob, 'A');
$result = $cl2();

// This will print Bob
echo $result;
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2
nakerlund at gmail dot com
6 months ago
I have two points:

It is possible to use Closure::fromCallable to convert private/protected methods to closures and use them outside the class.

Closure::fromCallable accepts late dynamic bindings using the keyword static if provided as a string.

My code below demonstrate how a private static method can be used as a callback in a function outside the class.

<?php
function myCustomMapper ( Callable $callable, string $str ): string {
  return
join(' ', array_map( $callable, explode(' ', $str) ) );
}

class
MyClass {

    public static function
mapUCFirst ( string $str ): string {
       
$privateMethod = 'static::mapper';
       
$mapper = Closure::fromCallable( $privateMethod );
        return
myCustomMapper( $mapper, $str );
    }
    private static function
mapper ( string $str ): string {
        return
ucfirst( $str );
    }

}

echo
MyClass::mapUCFirst('four little uncapitalized words');
// Prints: Four Little Uncapitalized Words
?>
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2
4-lom at live dot de
7 months ago
Sadly, your comparison is incorrect.

// The equivalent to
$cl1 = Closure::fromCallable("getName");
$cl1 = $cl1->bindTo($bob, 'A');

// is most likely this
$cl2 = function() {
    return call_user_func_array("getName", func_get_args());
};
$cl2 = $cl2->bindTo($bob, 'A');

Executing one or the other Closure should result in the same access violation error you already postet.

----
A simple PHP 7.0 polyfill could look like this:
----

namespace YourPackage;

/**
* Class Closure
*
* @see \Closure
*/
class Closure
{
    /**
     * @see \Closure::fromCallable()
     * @param callable $callable
     * @return \Closure
     */
    public static function fromCallable(callable $callable)
    {
        // In case we've got it native, let's use that native one!
        if(method_exists(\Closure::class, 'fromCallable')) {
            return \Closure::fromCallable($callable);
        }

        return function () use ($callable) {
            return call_user_func_array($callable, func_get_args());
        };
    }
}
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