Single-Case

Single-Case Switch in Go #

A single-case switch is the basic form of a switch statement where each case represents one specific value.

Syntax #

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

How it works: #

  1. The expression is evaluated once.
  2. Its value is compared with the values of each case.
  3. If a match is found, the associated block executes.
  4. The default keyword is optional and executes if no case matches.

Single-Case Switch Example #

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

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 code to run if there is no case match:

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

Important Note #

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

package main
import ("fmt")

func main() {
  a := 3

  switch a {
  case 1:
    fmt.Println("a is one")
  case "b": // ❌ Error: different type
    fmt.Println("a is b")
  }
}

Result:

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