Function Scope Basics

Part of the Fundamentals section of Coddy's GO journey — lesson 58 of 109.

In Go, variables declared inside a function are only accessible within that function. This is called function scope.

Create a function with a local variable:

func calculateTotal(price int, quantity int) int {
    tax := 0.1 * float64(price * quantity)  // local variable
    total := price * quantity + int(tax)
    return total
}

func main() {
    result := calculateTotal(10, 2)
    fmt.Println("Total:", result)
    // fmt.Println(tax)  // Error: tax is not accessible here
}

The output shows only the returned value:

Total: 22

The variable tax only exists inside the calculateTotal function and cannot be accessed from main.

Challenge

Beginner

In this challenge, you'll practice understanding function scope in Go. You need to fix a simple program that has a scope issue.

The program has a global variable message and a function that tries to modify it. Your task is to fix the code so that the function properly updates the global variable.

Cheat sheet

Variables declared inside a function are only accessible within that function (function scope):

func calculateTotal(price int, quantity int) int {
    tax := 0.1 * float64(price * quantity)  // local variable
    total := price * quantity + int(tax)
    return total
}

func main() {
    result := calculateTotal(10, 2)
    fmt.Println("Total:", result)
    // fmt.Println(tax)  // Error: tax is not accessible here
}

Local variables exist only within their function and cannot be accessed from outside.

Try it yourself

package main

import "fmt"

// Global variable
var message string = "Hello from global scope"

func updateMessage() {
    // This creates a new local variable instead of modifying the global one
    message := "Hello from function scope"
    fmt.Println("Inside function:", message)
}

func main() {
    fmt.Println("Before function call:", message)
    updateMessage()
    
    // TODO: The global message is still the original value
    // Modify the updateMessage() function to change the global variable
    fmt.Println("After function call:", message)
}