Why some developers create one method that returns new static? What is the reason to have a method that returns new static? I am not asking wha
get_called_class()).
class A {
public static function get_self() {
return new self();
}
public static function get_static() {
return new static();
}
}
class B extends A {}
echo get_class(B::get_self()); // A
echo get_class(B::get_static()); // B
echo get_class(A::get_self()); // A
echo get_class(A::get_static()); // A
new static
instantiates a new object from the current class, and works with late static bindings (instantiates the subclass if the class was subclassed, I expect you understand that).
Having a static
method on a class which returns a new instance of same is an alternative constructor. Meaning, typically your constructor is public function __construct
, and typically it requires a certain bunch of parameters:
class Foo {
public function __construct(BarInterface $bar, array $baz = []) { ... }
}
Having an alternative constructor allows you to provide different defaults, or convenience shortcuts to instantiate this class without having to supply those specific arguments and/or for being able to provide different arguments which the alternative constructor will convert to the canonical ones:
class Foo {
public function __construct(BarInterface $bar, array $baz = []) { ... }
public static function fromBarString($bar) {
return new static(new Bar($bar));
}
public static function getDefault() {
return new static(new Bar('baz'), [42]);
}
}
Now, even though your canonical constructor requires a bunch of complex arguments, you can create a default instance of your class, which will probably be fine for most uses, simply with Foo::getDefault()
.
The canonical example in PHP for this is DateTime
and DateTime::createFromFormat.
In your concrete example the alternative constructor doesn't actually do anything, so it's rather superfluous, but I expect that's because it's an incomplete example. If there's indeed an alternative constructor which does nothing other than new static
, it's probably just meant as convenience syntax over (new Foo)->
, which I find questionable.