Generics

There's no Tuple type available in Swift. If you wonder why that is, think about it: every tuple is a totally different type, depending on the types within it. So instead of defining a generic tuple requirement, you define the specific but generic incarnation of the tuple you intend to use:

func wantsTuple<T1, T2>(_ tuple: (T1, T2)) -> T1 {

     return tuple.0

}



wantsTuple((\"a\", \"b\")) // \"a\"

wantsTuple((1, 2)) // 1

You can also use tuples in typealiases, thus allowing subclasses to fill out your types with details. This looks fairly useless and complicated, but I've already had a use case where I need to do exactly this.

class BaseClass<A,B> {

     typealias Element = (A, B)

     func add(_ elm: Element) {

         print(elm)

     }

}



class IntegerClass<B> : BaseClass<Int, B> {

}



let example = IntegerClass<String>()

example.add((5, \"\"))

// Prints (5, \"\")

You can also define a typealias with generic parameters like in this example where we introduce a custom Either type:

typealias MyEither<A, B> = (left: A, right: B)