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Go switch

Use the switch statement to select one of many code blocks to be executed

The switch Statement

Use the switch statement to select one of many code blocks to be executed.

The switch statement in Go is similar to the ones in C, C++, Java, JavaScript, and PHP. The difference is that it only runs the matched case so it does not need a break statement.

Single-Case switch Syntax

Syntax

switch expression {
case x:
   // code block
case y:
   // code block
case z:
...
default:
   // code block
}

This is how it works:

  • The expression is evaluated once
  • The value of the switch expression is compared with the values of each case
  • If there is a match, the associated block of code is executed
  • The default keyword is optional. It specifies some code to run if there is no case match

    • Single-Case switch Example

    The example below uses a weekday number to calculate the weekday name:

    Example

    package main
    import ("fmt")

    func main() {
      day := 4

      switch day {
      case 1:
        fmt.Println("Monday")
      case 2:
        fmt.Println("Tuesday")
      case 3:
        fmt.Println("Wednesday")
      case 4:
        fmt.Println("Thursday")
      case 5:
        fmt.Println("Friday")
      case 6:
        fmt.Println("Saturday")
      case 7:
        fmt.Println("Sunday")
      }
    }

    Result:

    Thursday

    The default Keyword

    The default keyword specifies some code to run if there is no case match:

    Example

    package main
    import ("fmt")

    func main() {
      day := 8

      switch day {
      case 1:
        fmt.Println("Monday")
      case 2:
        fmt.Println("Tuesday")
      case 3:
        fmt.Println("Wednesday")
      case 4:
        fmt.Println("Thursday")
      case 5:
        fmt.Println("Friday")
      case 6:
        fmt.Println("Saturday")
      case 7:
        fmt.Println("Sunday")
      default:
        fmt.Println("Not a weekday")
      }
    }

    Result:

    Not a weekday

    All the case values should have the same type as the switch expression. Otherwise, the compiler will raise an error:

    Example

    package main
    import ("fmt")

    func main() {
      a := 3

      switch a {
      case 1:
        fmt.Println("a is one")
      case "b":
        fmt.Println("a is b")
      }
    }

    Result:

    ./prog.go:11:2: cannot use "b" (type untyped string) as type int

    Go Exercises

    Test Yourself With Exercises

    Exercise:

    Insert the missing parts to complete the following switch statement.

    package main   
import ("fmt") 
    
func main() {
  var day = 2
  switch  {
  (1):
    fmt.Print("Saturday")
  (2):
    fmt.Print("Sunday")    
  }
}

    Start the Exercise

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