Add pool-aware interface and trait

[garex]

Ok let's try here.

[michaelcullum]

@Crell Merge if you wish

[Crell]

I'm skeptical here. Certainly it can be done, but is it wise? How often will you be side-injecting a cache pool? It's not like the logger where it's more common to have a blanket "if it's loggable give it a logger" routine in your DI Container.

[garex]

@Crell how do you inject cache pool usually? As a constructor param?

I think cache is an often used feature, which can have it's own trait same as logger. Because it's a infrastructure layer.

[Crell]

Yes, constructor injection is preferred in virtually all cases. Setter injection is really only useful for cases like the logger, or maybe ContainerAware (which is usually a code smell), where an optional dependency can be passed in by a DI Container or factory selectively, based on the presence of an interface. The use cases for that pattern are, IMO, very slim, and I don't think cache is one of them. I'm actually hard pressed to think of any other than than ContainerAware or LoggerAware, now that I think of it...

[garex]

@Crell cache could be optional. That's why we have null-objects adapters both in stash and in symfony/cache.