Swift switch Statement

Swift Conditional Statements

The switch statement allows testing a variable against multiple values. In Swift, once a case is matched, the entire switch statement completes its execution.

Syntax

The syntax for the switch statement in Swift:

switch expression {
   case expression1:
      statement(s)
      fallthrough // Optional
   case expression2, expression3:
      statement(s)
      fallthrough // Optional

   default: // Optional
      statement(s);
}

The fallthrough statement is generally not used in switch statements.

It's important to note that if the fallthrough statement is not used in a case, the switch will terminate after executing the current case, and control flow will move to the next line following the switch statement.

If the fallthrough statement is used, it will continue executing the subsequent case or default statements, regardless of whether their conditions are met.

Note: In most languages, a break statement is required after each case in a switch block to prevent the subsequent cases from executing. However, in Swift, the execution does not continue by default. If you want the case statements to continue executing in Swift, you need to use the fallthrough statement.

Example 1

The following example does not use the fallthrough statement:

import Cocoa

var index = 10

switch index {
   case 100:
      print("index is 100")
   case 10, 15:
      print("index is 10 or 15")
   case 5:
      print("index is 5")
   default:
      print("default case")
}

When the above code is compiled and executed, it produces the following result:

index is 10 or 15

Example 2

The following example uses the fallthrough statement:

import Cocoa

var index = 10

switch index {
   case 100:
      print("index is 100")
      fallthrough
   case 10, 15:
      print("index is 10 or 15")
      fallthrough
   case 5:
      print("index is 5")
   default:
      print("default case")
}

When the above code is compiled and executed, it produces the following result:

index is 10 or 15
index is 5

Swift Conditional Statements