PHP 7.4.0RC4 Released!

Closure::fromCallable

(PHP 7 >= 7.1.0)

Closure::fromCallableConvertis un callable en une fermeture

Description

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

Crée et retourne une nouvelle fonction anonyme à partir du callable donnée en utilisant la portée courante. Cette méthode vérifie que callable est appelable dans la portée courante et émet un TypeError si ce n'est pas le cas.

Liste de paramètres

callable

Le callable à convertir.

Valeurs de retour

Retourne la nouvelle Closure créée ou émet une TypeError si callable n'est pas appelable dans la portée courante.

add a note add a note

User Contributed Notes 3 notes

up
17
igorchernin at yahoo dot com
2 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;
up
5
4-lom at live dot de
1 year 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());
        };
    }
}
up
4
nakerlund at gmail dot com
1 year 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
?>
To Top