Advanced Pattern Matching

Language Support

released Fri, 15 Feb 2019
Swift Version 5.0

Patterns with other Keywords

The Swift documentation points out, that not all patterns can be used with the if, for or the guard statement. However, the docs seem to be outdated. All 7 patterns work for all three keywords.

As a shorter example, see the Value Binding, Tuple, and Type Casting pattern used for all three keywords in one example:

// This is just a collection of keywords that compiles. This code makes no sense

func valueTupleType(a: (Int, Any)) -> Bool {

     // guard case Example

     guard case let (x, _ as String) = a else { return false}


     // for case example

     for case let (a, _ as String) in [a] {



     // if case example

     if case let (x, _ as String) = a {

        print(\"if\", x)


     // switch case example

     switch a {

     case let (a, _ as String):


         return true

     default: return false



With this in mind, we will have a short look at each of those keywords in detail.