On Mon, Sep 19, 2011 at 10:40 AM, Gustavo Lopes <glo...@nebm.ist.utl.pt> wrote:
> Em Sun, 18 Sep 2011 20:06:31 +0100, Stas Malyshev <smalys...@sugarcrm.com>
> escreveu:
>
>> On 9/18/11 11:23 AM, Nikita Popov wrote:
>>>
>>> to tell you: I need this and that method accepting these and these
>>> arguments to work correctly. If the signature isn't enforced, this
>>> doesn't make sense anymore. You could just as well drop the signature
>>> from abstract method definitions, as it's pointless then.
>>
>> No it is not. The signature tells "this method would accept certain
>> arguments". If you call it with these arguments, it would work. However,
>> there's no promise to never extend the cases where it works - it goes
>> contrary to the whole point of OOP to say "I will never loosen preconditions
>> on my methods".
>
> While this is true, we should be a bit pragmatic here.
>
> If the subclass method specifies less parameters, it is very likely a
> mistake. It's not usual (certainly it's not more frequent than a mistake
> being the case) for arguments to be simply intentionally ignored. In fact, I
> don't know of any popular language that implements this type of
> contravariance. Plus, consider the case in which the superclass takes an
> argument by reference:
>
> function increment(&$foo) { $foo = $foo + 1; }
>
> It is obvious that in this case a subclass override that takes no arguments
> cannot possibly satisfy the contract of the original method. That is to say,
> by ref arguments are also used for postconditions.
>
> That said, I think the only rules worth implementing are:
>
> * Allow arguments with a supertype. For instance, this should give no
> warning:
>
> <?php
> class A {}
> class B extends A {}
> class C { function g(B $b) {} }
> class D extends C { function g(A $a) { } }
>
> * Allow extra parameters with a default value (implemented):
>
> <?php
> class C { function g($a) {} }
> class D extends C { function g($a,$b=true) { } }
>could you check my second(lengthy) mail on this thread? I also tried to come up with the valid, and invalid signature changes. I forget to take references into account, so thanks for pointing that out. -- Ferenc Kovács @Tyr43l - http://tyrael.hu -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
