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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
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