Re: [RFC] Traits with interfaces

On Wed, Feb 17, 2016 at 12:48 PM, Kevin Gessner <kgessner@etsy.com> wrote: > On Wed, Feb 17, 2016 at 10:26 AM, Levi Morrison <levim@php.net> wrote: >> >> I want to add my personal experience with traits: every time I create >> a trait it is to implement an interface. Here is a publicly available >> [example with >> >> OuterIterator](https://github.com/morrisonlevi/Ardent/blob/master/src/Collection/OuterIteratorTrait.php): >> >> [snip] >> >> I can see how it would be nice to allow the trait to officially >> declare that it implements some interface (in this case Iterator or >> OuterIterator) which would require that the trait has fully >> implemented the required methods (or declared them as abstract). This >> would be a small improvement but helpful. >> >> I am less certain about the classes which use it >> automatically >> inheriting the interfaces. To clarify: I am neither in favor or >> against that part. Or at least at this stage, anyway. > > > I don't think there is enough benefit from allowing traits to declare > interfaces, but not propagating the interface out to classes that insert the > trait. It does provide an extra bit of enforcement on the trait's methods, > but the real value is in making that contract a part of the classes. I do agree that there is only a little benefit but I disagree that it is "not enough". It's a quality of life change to an existing feature that has no impact outside of that feature – sounds perfect to me. > In what situation would a class that inserts OuterIterator not want to > declare the Iterator class? If every class that inserts the trait would > also declare Iterator, it's needless repetition to require that both the > class and the interface. Funny you should ask, because OuterIteratorTrait implementing OuterIterator is actually a case where not all using classes will want to be OuterIterators formally (just get the horizontal code reuse). This is because I don't want to "leak" the inner iterator because it is suppose to be abstracted. In these cases I use the syntax for using a trait method under a different visibility.