Switch statement in Go

Introduction

A switch statement helps you choose between many options easily. It makes your code cleaner than many if-else checks.

When you want to run different code based on a variable's value.

When you have many conditions to check against one value.

When you want clearer code instead of many if-else statements.

Syntax

Go

switch variable {
case value1:
    // code to run if variable == value1
case value2:
    // code to run if variable == value2
default:
    // code to run if no case matches
}

The default case runs if no other case matches.

You don't need to write break in Go; it stops automatically after a case.

Examples

This checks the day and prints a message for Monday, Friday, or any other day.

Go

switch day {
case "Monday":
    fmt.Println("Start of the week")
case "Friday":
    fmt.Println("Almost weekend")
default:
    fmt.Println("Just another day")
}

This switch uses conditions without a variable to check age ranges.

Go

switch {
case age < 13:
    fmt.Println("Child")
case age < 20:
    fmt.Println("Teenager")
default:
    fmt.Println("Adult")
}

Sample Program

This program checks the fruit variable and prints a message based on its value.

Go

package main

import "fmt"

func main() {
    fruit := "apple"

    switch fruit {
    case "apple":
        fmt.Println("This is an apple.")
    case "banana":
        fmt.Println("This is a banana.")
    default:
        fmt.Println("Unknown fruit.")
    }
}

Important Notes

Go's switch stops automatically after a matching case; no need for breaks.

You can use switch without a variable to check conditions directly.

Use default to handle unexpected cases.

Summary

Switch helps pick one action from many choices.

It makes code easier to read than many if-else statements.

Go switch automatically stops after a case runs.

Practice

1. What does a switch statement do in Go?

easy

A. It selects one case to run based on a value.

B. It repeats code multiple times like a loop.

C. It defines a new function.

D. It declares a variable.

Solution

1. Step 1: Understand the purpose of switch

   A switch statement chooses one path among many based on a value.

2. Step 2: Compare with other options

   Loops repeat code, functions define behavior, variables store data. Switch picks cases.

3. Final Answer:

   It selects one case to run based on a value. -> Option A

4. Quick Check:

   Switch = Select case [OK]

Hint: Switch picks one matching case to run [OK]

Common Mistakes:

• Confusing switch with loops
• Thinking switch defines functions
• Believing switch declares variables

2. Which of the following is the correct syntax for a basic switch statement in Go?

easy

A. switch (x) { case 1: fmt.Println("One") default: fmt.Println("Other") }

B. switch x { case 1: fmt.Println("One") default: fmt.Println("Other") }

C. switch x: case 1: fmt.Println("One") default: fmt.Println("Other")

D. switch x { case 1 => fmt.Println("One") default => fmt.Println("Other") }

Solution

1. Step 1: Recall Go switch syntax

   Go uses switch variable { case value: ... default: ... } without parentheses.

2. Step 2: Check each option

   switch x { case 1: fmt.Println("One") default: fmt.Println("Other") } matches correct syntax. switch (x) { case 1: fmt.Println("One") default: fmt.Println("Other") } wrongly uses parentheses. switch x: case 1: fmt.Println("One") default: fmt.Println("Other") uses colon after switch. switch x { case 1 => fmt.Println("One") default => fmt.Println("Other") } uses => which is invalid.

3. Final Answer:

   switch x { case 1: fmt.Println("One") default: fmt.Println("Other") } -> Option B

4. Quick Check:

   Correct syntax = switch x { case 1: fmt.Println("One") default: fmt.Println("Other") } [OK]

Hint: No parentheses around switch variable in Go [OK]

Common Mistakes:

• Adding parentheses around switch variable
• Using colon after switch keyword
• Using => instead of colon in cases

3. What will be the output of this Go code?

package main
import "fmt"
func main() {
  x := 2
  switch x {
  case 1:
    fmt.Println("One")
  case 2:
    fmt.Println("Two")
  case 3:
    fmt.Println("Three")
  default:
    fmt.Println("Other")
  }
}

medium

A. Two

B. Three

C. One

D. Other

Solution

1. Step 1: Identify the switch variable and value

   The variable x is 2.

2. Step 2: Match the case with value 2

   The case 2 matches and prints "Two".

3. Final Answer:

   Two -> Option A

4. Quick Check:

   Switch x=2 prints "Two" [OK]

Hint: Match switch value to case label [OK]

Common Mistakes:

• Choosing default instead of matching case
• Confusing case numbers
• Ignoring switch variable value

4. Find the error in this Go switch code:

package main
import "fmt"
func main() {
  x := 3
  switch x {
  case 1
    fmt.Println("One")
  case 2:
    fmt.Println("Two")
  default:
    fmt.Println("Other")
  }
}

medium

A. fmt.Println syntax error

B. Missing default case

C. Switch variable must be string

D. Missing colon after case 1

Solution

1. Step 1: Check case syntax

   Each case must end with a colon (:). Here, case 1 misses the colon.

2. Step 2: Verify other parts

   Default case exists, switch variable can be int, fmt.Println is correct.

3. Final Answer:

   Missing colon after case 1 -> Option D

4. Quick Check:

   Case syntax requires colon [OK]

Hint: Each case must end with a colon (:) [OK]

Common Mistakes:

• Omitting colon after case
• Thinking default is mandatory
• Assuming switch variable must be string

5. How can you write a Go switch statement that prints "Weekend" for Saturday and Sunday, and "Weekday" for other days (1=Monday, 7=Sunday)?

hard

A. switch day {
case day == 6 || day == 7:
fmt.Println("Weekend")
default:
fmt.Println("Weekday")
}

B. switch day {
case 6:
fmt.Println("Weekend")
case 7:
fmt.Println("Weekday")
default:
fmt.Println("Weekday")
}

C. switch day {
case 6, 7:
fmt.Println("Weekend")
default:
fmt.Println("Weekday")
}

D. switch day {
case 6:
fmt.Println("Weekend")
case 7:
fmt.Println("Sunday")
default:
fmt.Println("Weekday")
}

Solution

1. Step 1: Group weekend days in one case

   Using case 6, 7: groups Saturday and Sunday together.

2. Step 2: Use default for other days

   Default prints "Weekday" for days 1 to 5.

3. Final Answer:

   switch day { case 6, 7: fmt.Println("Weekend") default: fmt.Println("Weekday") } -> Option C

4. Quick Check:

   Multiple values in one case = switch day { case 6, 7: fmt.Println("Weekend") default: fmt.Println("Weekday") } [OK]

Hint: Use commas to group cases in Go switch [OK]

Common Mistakes:

• Separating weekend days into different cases with wrong output
• Using logical OR inside switch expression incorrectly
• Missing default case for weekdays