如何在Swift中构造通用类型协议一致性？

Question

The following contrived Swift 2 example from real-world code won't compile:

protocol SomeModelType {  }

protocol SomeProtocol {
    var someVar: SomeModelType? { get }
}

class ConcreteClass<T: SomeModelType>: SomeProtocol {
    var someVar: T?
}

This doesn't make sense to me fully. I would assume in ConcreteClass that because I have T being constrained to SomeModelType and have T as the backing type for the someVar property, the compiler would be able to figure out that the SomeProtocol was being conformed to by ConcreteClass .

How should an example like this be structured? Is it possible to the Swift compiler to determine protocol conformance through generic type constraints?

Answer 1

protocol SomeModelType {  }

protocol SomeProtocol {

    associatedtype T: Any
    var someVar: T? { get }
}

class ConcreteClass<T> :SomeProtocol where T: SomeModelType {

    var someVar: T?

}