Advanced Pattern Matching


released Fri, 15 Feb 2019
Swift Version 5.0


Swift's switch statement bears little resemblance to the similarly named equivalent in C or Objective-C. Even though they share the same name, the Swift version can do much, much more.

In the following guide, I will try to explain the various usages for these new features in more detail.

The main feature of switch is, of course, pattern matching: the ability to destructure values and match different switch cases based on correct match of the values to the cases.


Destructuring means to take something of a certain structure and destructure it into smaller items again. Imagaine you had a lnk::tuple variable user with the following value: (firstname: "Harry", lastname: "Potter", age: 21, occupation: "Wizard")

Destructuring means taking this tuple and converting it into individual variables:

let harry = (firstname: \"Harry\", lastname: \"Potter\", age: 21, occupation: \"Wizard\")

let (name, surname, age, occupation) = harry


Destructuring is a great method for handling the information in complex types. It is also a fundamental part of Swift's switch statement. The next step, then, is to have a look at switch:

A simple example

We wrote a game where both players have to take a quiz. After each question we evaluate who won or lost. There're four states:

  • Player 1 is correct
  • Player 2 is correct
  • Both were correct
  • Both were wrong

We can model this logic very nicely with a switch statement such as the following:

let player1 = true

let player2 = false

switch (player1, player2) {

case (true, false): print(\"Player 1 won\")

case (false, true): print(\"Player 2 won\")

case (true, true): print(\"Draw, both won\")

case (false, false): print(\"Draw, both lost\")


Here, we create a tuple (player1, player2) and then match each of the possible cases.

This was a very short introduction, now we will go into more detail.