Instantiate an object of a generic type in Swift

Question

I am implementing a class Foo in Swift, that is supposed to instantiate objects of a given subclass of SuperBar, e.g. Bar: SuperBar. I really like generics in Swift, so I tried implementing it this way:

class Foo<T: SuperBar> {

    func instantiateObject() -> T {
        return T()
    }

}

class SuperBar {

}

class Bar: SuperBar {

}

let foo = Foo<Bar>()

let obj = foo.instantiateObject()

You can run the code snippet in an Xcode Playground and observe that obj is of type SuperBar instead of Bar, although it says Bar when I Alt-click on the constant name.

Any Ideas? :)

Answer 1

Mark the class init as required and then call init :

class SuperBar {
    required init() {
    }
}


class Foo<T: SuperBar> {

    func instantiateObject() -> T {
        return T.init()
    }

}