Switch statement in Go - Mini Project: Build & Apply

Using Switch Statement in Go

📖 Scenario: You are creating a simple program that tells the type of day based on a number input. This is like checking the day of the week where 1 means Monday, 2 means Tuesday, and so on.

🎯 Goal: Build a Go program that uses a switch statement to print the name of the day for numbers 1 to 7. If the number is not between 1 and 7, print "Invalid day".

📋 What You'll Learn

Create a variable dayNumber with an integer value.

Create a switch statement using dayNumber.

Use case blocks for numbers 1 to 7 to print the correct day name.

Use default case to print "Invalid day" for other numbers.

💡 Why This Matters

🌍 Real World

Switch statements are used in many programs to choose actions based on different values, like menu selections or day names.

💼 Career

Understanding switch statements helps in writing clear and efficient code for decision making in software development jobs.

1

Create the dayNumber variable

Create an integer variable called dayNumber and set it to 3.

Go

// Create an integer variable called dayNumber and set it to 3
// Your code here

Hint

Use := to declare and assign the variable in one line.

2

Start the switch statement

Add a switch statement using the variable dayNumber inside the main function.

Go

package main

func main() {
    dayNumber := 3
    // Start a switch statement with dayNumber
    // Your code here
}

Hint

Write switch dayNumber { to start the switch block.

3

Add cases for days 1 to 7 and default

Inside the switch dayNumber, add case blocks for numbers 1 to 7. Use fmt.Println to print the day names: 1 - Monday, 2 - Tuesday, 3 - Wednesday, 4 - Thursday, 5 - Friday, 6 - Saturday, 7 - Sunday. Add a default case to print "Invalid day".

Go

package main

import "fmt"

func main() {
    dayNumber := 3
    switch dayNumber {
        // Add case 1 to 7 with fmt.Println for day names
        // Add default case to print "Invalid day"
        // Your code here
    }
}

Hint

Each case ends with a colon and the code to run is indented below it.

4

Print the result

Run the program to print the day name for dayNumber. The output should be Wednesday.

Go

package main

import "fmt"

func main() {
    dayNumber := 3
    switch dayNumber {
    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")
    }
    // Run the program to print the day name
    // Your code here
}

Hint

Just run the program. It will print the day name automatically.

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