AnyObject vs. Struct (Any)

Question

I would like to create a method like this for my projects:

func print(obj: AnyObject) {
    if let rect = obj as? CGRect {
        println(NSStringFromCGRect(rect))
    }
    else if let size = obj as? CGSize {
        println(NSStringFromCGSize(size))
    }

    //...
}

But I can't because CGRect and CGSize are structs and do not conform to the AnyObject protocol. So, any ideas on how this could be done?

Answer 1

Use Any instead of AnyObject.

Swift provides two special type aliases for working with non-specific types:

• AnyObject can represent an instance of any class type.
• Any can represent an instance of any type at all, including function types.

The Swift Programming Language

Answer 2

@nkukushkin's answer is correct, however, if what you want is a function that behaves differently depending on whether it’s passed a CGRect or a CGStruct, you are better off with overloading:

func print(rect: CGRect) {
    println(NSStringFromCGRect(rect))
}

func print(size: CGSize) {
    println(NSStringFromCGSize(size))
}

In comparison, the Any will be both inefficient (converting your structs to Any and back, could have a big impact if you do this a lot in a tight loop), and non-typesafe (you can pass anything into that function, and it will only fail at runtime).

If your intention is to coerce both types into a common type and then do the same operation on it, you can create a 3rd overload that takes that type, and have the other two call it.