Swift - what's the difference between metatype .Type and .self?

Question

What\'s the difference between metatype .Type and .self in Swift?

Do .self and .Type return a struct

Answer 1

This was one of those topics that confused the hell out of me today.

I was writing a generic function:

func foo(ofType: T.Type) {
    T.bar()
}

And tried calling it as follows:

foo(ofType: ClassImplementingProtocol.Type) // Compiler error

Spent about 30 min researching why it wasn't working. Then I tried this:

foo(ofType: ClassImplementingProtocol.self) // Works

Turns out Xcode's code completion is very bad at showing the difference between meta types and types... From the code completion pop-up it looks like .self and .Type are the same thing:

But the "explain like im 5" of it is, when you have a method parameter of Class.Type, it is expecting an instance of Class.Type.

Class.self returns an instance of Class.Type, whereas Class.Type is referring to Class.Type...

Very unclear if you ask me.