I've felt the need for this for some time.
Proposed syntax:
-------------------------
$x = (InterfaceName) $container->service;
Proposed behavior:
---------------------------
Checks if the instance if an instance of the given class/interfaces. If yes,
does nothing, if not, issues a fatal error. Pseudo code:
$temp = $container->service;
if ($temp instanceof InterfaceName) {
$x = $temp;
} else {
trigger_error('The object can not be cast to InterfaceName');
}
Use cases:
----------------
As my example hints, the intent is to provide type safety and hinting for the
increasingly used dependency injection container pattern.
It's useful to provide type safety also for all similar patterns which may not
return a result of the expected type: Registry, ServiceLocator, Factory etc.
Additionally to runtime type safety, this will also serve to editors/IDEs as an
inline hint to provide proper autocompletion, i.e. instead of this:
/** @var $foo InterfaceName */
$foo = $container->service;
People can now just write:
$foo = (InterfaceName) $container->service;
Alternative syntax:
--------------------------
I realize "casting" isn't a perfect match as the behavior is equivalent to
inline type hinting. On the other hand, casting and inline type hinting in
dynamic languages often behave identically (see the casting behavior in
ActionScript which combines type hints with a JS-like dynamic type system).
And this syntax doesn't introduce new keywords. Still, alternative ways to
implement this could be:
1. $foo = $container->service as InterfaceName;
2. $foo = $container->service is InterfaceName;
3. $foo = (InterfaceName $container->service);
4. InterfaceName $foo = $container->service;
All of those would be fine, especially 4, which has precedent in other
languages, and in PHP as well with typehinting and in catch blocks: catch
(ClassName $e) { ... }
I'm ok with suggestions for any syntax that is as short, if it fits the
behavior better.
Feedback?
Stan
