Closure::fromCallable

(PHP 7 >= 7.1.0)

Closure::fromCallable — Bir işlevi bir closure yöntemine dönüştürür

Açıklama

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

Geçerli bağlamı kullanarak callback bağımsız değişkeninde belirtilen işlevden yeni bir anonim işlev oluşturur ve döner. Bu yöntem callback işlevinin geçerli bağlamda çağrılabilirliğini sınar ve çağrılabilir değilse bir TypeError yavrular.

Bilginize:
PHP 8.1.0 itibariyle, Birinci sınıf çağrılabilir sözdizimine bu yöntemle aynı sözdizimsel kurallar uygulanmaktadır.

Bağımsız Değişkenler

callback: Dönüştürülecek işlev.

Dönen Değerler

callback işlevi geçerli bağlamda çağrılabiliyorsa yeni oluşturulan Closure ile, çağrılamıyorsa bir TypeError ile döner.

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User Contributed Notes 3 notes

down

igorchernin at yahoo dot com ¶

7 years 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;

down

4-lom at live dot de ¶

6 years 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());
        };
    }
}

down

nakerlund at gmail dot com ¶

6 years 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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