How to use AnyClass in Swift Generic class

Question

I need to pass a type in my generic base class.

class SomeBaseClass<T: AnyClass> {
   // Implementation Goes here
}

I get the following error:

Inheritance from non-protocol, non-class type 'AnyClass' (aka 'AnyObject.Type')

Ideally I would like to use 'T' to be as a specific type rather than AnyClass, but AnyClass is OK as well.

Thanks

Answer 1

You should use AnyObject if you want the type to be a class.

class SomeBaseClass<T: AnyObject> {
    // Implementation Goes here
}

// Legal because UIViewController is a class
let o1 = SomeBaseClass<UIViewController>()

// Illegal (won't compile) because String is a struct
let o2 = SomeBaseClass<String>()

Answer 2

Instead of specifying T needs to be a class, you could instead do:

class SomeBaseClass<T> {
    let type: T.Type

    init(type: T.Type) {
        self.type = type
    }
}

If you're planning to be using T.Type a lot it may be worth using a typealias:

class SomeBaseClass<T> {
    typealias Type = T.Type
    let type: Type
    ...
}

Some example usage:

let base = SomeBaseClass(type: String.self)

And advantage of this method is T.Type could represent structs and enums, as well as classes.