Re: Traits expecting interfaces implicitly leads to expensive runtime checks

Hi: I added the proposal to the RFC. See http://wiki.php.net/rfc/horizontalreuse#requiring_composing_class_to_implement_interface ===== Requiring Composing Class to Implement Interface ===== Traits are able to express required methods by using abstract method declarations. An abstract method can be satisfied in varios ways, for instance by implementing it in the composing class or by bringing it in from another Trait. However, for traits that require complex interfaces to be satisfied, this approach is tedious and fragile, since it requires the developer to state all used methods explicitly. Another solution is that a Trait expresses a requirement for the composing class to implement a certain interface. This is not entirely identical to using abstract methods, however. First, it imposes a requirement on interface level and thus will have the same fragility with respect to interface changes as all other clients of an interface. On the other hand, it avoids duplications of abstract method definitions and makes the interface the main entity of responsibility as for normal client-interface uses in current code. <?php // IteratorUser works with $this using the Iterator interface trait IteratorUser require Iterator { function foo() { $next = $this->next(); ... } } // composed into a class that needs to implement the interface class Example implements Iterator { use IteratorUser; } Are there any objections to implementing this? Thanks Stefan -- Stefan Marr Software Languages Lab Vrije Universiteit Brussel Pleinlaan 2 / B-1050 Brussels / Belgium http://soft.vub.ac.be/~smarr Phone: +32 2 629 2974 Fax: +32 2 629 3525