switch and fallthrough

Learn multi-branch switch and the fallthrough behavior.

switch and fallthrough

switch compares a value against several possibilities. A case can take several values separated by commas; the switch ends when the matching case finishes:

switch gun {
case "Cumartesi", "Pazar":
    fmt.Println("hafta sonu")
case "Cuma":
    fmt.Println("son iş günü")
default:
    fmt.Println("iş günü")
}

To deliberately continue into the next case write fallthrough; it is rarely needed.

Expressionless switch

A switch without a value is a readable form of a long if-else chain; each case is a bool expression:

switch {
case sicaklik < 0:
    fmt.Println("donuyor")
case sicaklik < 20:
    fmt.Println("serin")
default:
    fmt.Println("sıcak")
}

Cases are tried from top to bottom; the first true one runs.

Exercise Kind of day

Write gunTuru(gun string) string: "hafta sonu" for "Cumartesi" and "Pazar", "iş günü" otherwise. Print gunTuru("Pazar") and gunTuru("Salı") on one line.

Show example solution

package main

import "fmt"

func gunTuru(gun string) string {
    switch gun {
    case "Cumartesi", "Pazar":
        return "hafta sonu"
    default:
        return "iş günü"
    }
}

func main() {
    fmt.Println(gunTuru("Pazar"), gunTuru("Salı"))
}

Test yourself

Does <code>fallthrough</code> check the next case's condition?
- It runs all cases
- It jumps to default
- No; it runs the next case's body without checking its condition
- Yes, it runs it if the condition is true
Show answer

No; it runs the next case's body without checking its condition — fallthrough is an unconditional jump; that's why it can cause surprising behavior and is used carefully.

Multiple values

switch gun {
case "Cumartesi"____ "Pazar":
    fmt.Println("hafta sonu")
}

Show answer

switch gun {
case "Cumartesi", "Pazar":
    fmt.Println("hafta sonu")
}

Input and output

"Pazar"

hafta sonu
"Cuma"

son iş günü
"Salı"

iş günü (default)
sicaklik = -3

donuyor

Next lesson: break and continue

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