The switch statement in Go is a control structure used for selecting one block of code to execute from multiple options. Unlike some other programming languages such as C, C++, Java, JavaScript, and PHP, Go’s switch statement does not require a break statement to exit a case, as it automatically terminates after executing the matched case.
Single-Case switch Syntax
switch expression {
case x:
// code block
case y:
// code block
case z:
// code block
default:
// code block
}
How It Works:
- The
expressionis evaluated once. - The value of the
expressionis compared with the value in eachcase. - If a match is found, the associated code block executes.
- The
defaultblock (optional) will execute if no case matches.
Example 1: Weekday Calculation
package main
import ("fmt")
func main() {
day := 3
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("Invalid day")
}
}
Output (if day = 3):
Wednesday
Example 2: Motorcycle Brand Selector
package main
import ("fmt")
func main() {
model := "Ducati"
switch model {
case "Yamaha":
fmt.Println("You selected Yamaha. Known for performance and reliability.")
case "Honda":
fmt.Println("You selected Honda. A favorite for its versatility.")
case "Suzuki":
fmt.Println("You selected Suzuki. Renowned for stylish designs.")
case "Ducati":
fmt.Println("You selected Ducati. Famous for its speed and luxury.")
default:
fmt.Println("Unknown brand. Please choose a valid motorcycle.")
}
}
Output (if model = "Ducati"):
You selected Ducati. Famous for its speed and luxury.
The default Keyword
The default keyword provides a fallback option when no case matches. For example:
package main
import ("fmt")
func main() {
day := 10
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("Invalid day")
}
}
Output (if day = 10):
Invalid day
Example 3: Type Check Error
Ensure all case values are of the same type as the switch expression. Mixing types will result in a compilation error. Here’s an illustration:
package main
import ("fmt")
func main() {
engineType := 4
switch engineType {
case 1:
fmt.Println("Engine type is single-cylinder.")
case "v-twin":
fmt.Println("Engine type is a v-twin.") // This will cause an error!
}
}
Result:
./prog.go:11:2: cannot use "v-twin" (type untyped string) as type int
