I have to pass an interface as a parameter to a function. Interface is generic a.k.a. has a associated type. I couldn't find a good way to do that. Here is my code:
protocol IObserver : class {
typealias DelegateT
...
}
class Observer: IObserver {
typealias DelegateT = IGeneralEventsDelegate // IGeneralEventsDelegate is a protocol
...
}
func notify(observer: IObserver) { ... } // here I need a type for observer param
I found that this will work:
func notify<T: IObserver where T.DelegateT == IGeneralEventsDelegate>(observer: T) { ... }
, but come on that is too complicated. What if I want to save this param in class variable, should I make the whole class generic, just because of this function.
It is true that I'm C++ developer and I'm new to the Swift language, but the way the things are done are far too complicated and user unfriendly ... or I'm too stupid :)
If you use typealias in a protocol to make it generic-like, then you cannot use it as a variable type until the associated type is resolved. As you have probably experienced, using a protocol with associated type to define a variable (or function parameter) results in a compilation error:
Protocol 'MyProtocol' can only be used as a generic constraint because it has Self os associated type requirements
That means you cannot use it as a concrete type.
So the only 2 ways I am aware of to use a protocol with associated type as a concrete type are:
See also related answer https://stackoverflow.com/a/26271483/148357
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