On Mon, Oct 17, 2011 at 8:19 PM, Ferenc Kovacs <tyr...@gmail.com> wrote:
> > > On Mon, Oct 17, 2011 at 8:00 PM, Stefan Marr <p...@stefan-marr.de> wrote: > >> Hi Ferenc: >> >> On 17 Oct 2011, at 19:41, Ferenc Kovacs wrote: >> >> > Hi Stefan, >> > >> > Multiple people asked me that how they can expect/check that a given >> object uses a trait or not. >> > Of course one could write the concrete methods as a trait and always use >> a given interface for typehints, but I can't see why shouldn't instanceof >> and typehints in general work for traits. >> > Is the any technical or maybe theoretical argument against this? >> >> Originally I proposed traits including the semantics that traits directly >> implement interfaces. >> >> The discussion is somewhere here: >> http://www.mail-archive.com/internals@lists.php.net/msg33935.html >> >> I think Sebastian was the person with the strongest opinion on that >> particular issue: >> http://www.mail-archive.com/internals@lists.php.net/msg33948.html >> >> And I tend to agree with him. >> >> Currently I think along the following lines: >> >> A trait is not a full unit of reuse! >> A class is. >> Don't use traits where you should use classes and composition. >> Traits do not guarantee anything, if you want to be sure your invariants >> hold, use classes and composition. >> >> Traits allow to reuse behavior in a much more flexible way, but they do >> not replace classes. >> >> And, well, then there is this: >> https://wiki.php.net/rfc/horizontalreuse#requiring_composing_class_to_implement_interface >> >> That should make sure that people can use interfaces for the purpose >> envisioned here. >> >> For reference, there is also: https://bugs.php.net/bug.php?id=55613 >> >> >> But aside of the things I said before: >> - theoretically: keeping interfaces and traits apart is a good, clean >> language design decision. >> - practically: people LOVE ugly languages, because they get things done >> >> So, well, I can't claim anything about value here. >> The current situation might be more friendly to the teacher. >> Another design might offer more freedom/power... > > > Thanks for the clarification. > Without either having the ability to check a trait or implement an > interface for a trait, or at least implementing the require syntax, I think > that it isn't really a non-fragile solution for my question. > AFAIK the only solution available currently is something like: > > <?php > interface testTraitInterface{ > > } > > trait testTrait{ > > } > > class testClass implements testTraitInterface{ > use testTrait; > } > > $tc = new testClass; > var_dump($tc instanceof testTraitInterface); > > > Which is pretty weak of a solution, however if we only thinks traits as a > macro, this is enough, but then why bother with the as and insteadof, traits > composed traits and such? > I think we will have much more feedback with the release of 5.4, so maybe > we can re-consider extending the implementation for the next version. > And I agree that it is the best to only release what we are confident in, > and I'm happy that we waited a version for correctly implementing Closures > for objects. > > Thanks again for the clarification and for your work on traits! > Jeff Carouth pointed out( https://twitter.com/#!/jcarouth/status/126030715514138624) that we have class_uses() (https://bugs.php.net/bug.php?id=55266), would be nice having that in the documentation. -- Ferenc Kovács @Tyr43l - http://tyrael.hu
