At 09:31 AM 4/19/2004 -0700, Sterling Hughes wrote:
I agree. Interfaces are useless if you can't guarantee that a class actually implements them. Violating an interface is violating a contract and it should be an compile error - indeed, when coding I mostly rely on not properly implementing interfaces to be a compile error.
-Sterling
-----Original Message----- From: Zeev Suraski [mailto:[EMAIL PROTECTED] Sent: Monday, April 19, 2004 1:49 AM To: [EMAIL PROTECTED] Subject: [PHP-DEV] Interface inheritance
All,
Yesterday, someone complained that classes that implement interfaces succeed in doing so even when they don't satisfy the prototypes. While this does cause an E_STRICT message to be emitted, it would go unnoticed in most cases, as E_STRICT is off by default, in some cases - even when people think it's on.
I believe that this behavior is wrong. I believe that classes should not be allowed to say they implement an interface X, unless they actually implement all of the methods in that interface with methods that are compatible with its prototypes.
Reasoning: - Interfaces (and for that matter, abstract classes) are a new feature in PHP 5, used solely to enforce implementing classes to abide to the prototypes. There's no issue of downwards compatibility, and there's no other use case. - Without this, the whole mechanism of class type hints is rendered useless. With it, it gives users the full power of class type hints (and instanceof, for that matter) - because they always have the option of adding an interface for their base classes.
Suggested behavior: Any method that implements (directly or indirectly) an interface method or an abstract method, will have implementation checks fully enforced, with an E_COMPILE_ERROR emitted in case of an error. Behavior for methods that override regular parent methods, that do not have interface/abstract prototypes, will not change (E_STRICT message).
Comments welcome - we'd like to sort this out before RC2...
Zeev
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