Generic functions

In Swift, the simplest form of generics would be the generics in functions. You can use generics very simply, with angled brackets, as follows:

func concat<T>(a: T, b: T) -> [T] {
    return [a,b]
}

The concat method knows nothing about the types that you are passing in, but generics gives us many guarantees over using Any:

• a and b should be of the same type
• The return type is an array of elements that have the same type as a and b
• The type is inferred from the context so you don't have to type it in when you code

You can also leverage protocol conformance in your generic functions, as follows:

protocol Runnable {
    func run()
}

func run<T>(runnable: T) where T: Runnable {
    runnable.run()
}

In this case, the method that is run can only be called with an object that is Runnable.