Variable Shadowing in `if`

Part of the Fundamentals section of Coddy's GO journey — lesson 37 of 109.

Let's learn about variable shadowing in if statements. This allows you to create a variable that only exists within the if block and its related else blocks.

First, let's create a variable outside our conditional statement:

x := 10
fmt.Println("Original x value:", x)

After executing this code, we'll have a variable x with the value 10 that we can use throughout our program.

Now, let's use variable shadowing in an if statement to create a new variable that only exists within that block:

if y := x * 2; y > 15 {
    fmt.Println("y is greater than 15:", y)
    // y only exists in this block
} else {
    fmt.Println("y is not greater than 15:", y)
    // y is also available in else blocks
}

After executing this code, Go will calculate y as 20 (which is x * 2), check if it's greater than 15, and then execute the first block. The output will show on the screen:

y is greater than 15: 20

Finally, let's try to access our variables after the if statement:

// fmt.Println(y) would cause an error - y doesn't exist here
fmt.Println("x is still:", x)

After executing this code, we can still access x, but y is no longer available because it only existed within the if and else blocks. The output will show on the screen:

x is still: 10

This demonstrates how variable shadowing works in if statements - the variable y is only accessible within the conditional blocks where it was declared.

Challenge

Beginner

In this challenge, you'll practice variable shadowing in an if statement. You'll see how a variable declared inside an if block can have the same name as a variable in the outer scope, but with a different value.

The code has a variable message in the outer scope. Your task is to create a shadowed variable with the same name inside the if block and then print both variables to see the shadowing effect.

Cheat sheet

Variable shadowing in if statements allows you to create variables that only exist within the conditional block and its related else blocks.

Syntax for variable shadowing in if statements:

if variable := expression; condition {
    // variable only exists in this block
} else {
    // variable is also available in else blocks
}

Example:

x := 10
if y := x * 2; y > 15 {
    fmt.Println("y is greater than 15:", y)
} else {
    fmt.Println("y is not greater than 15:", y)
}
// y is no longer accessible here
fmt.Println("x is still:", x)

The shadowed variable is only accessible within the if and else blocks where it was declared, not outside of them.

Try it yourself

package main

import "fmt"

func main() {
	// Outer scope variable
	message := "Hello from outer scope"
	
	isLoggedIn := true
	
	if isLoggedIn {
		// TODO: Create a new variable named 'message' with the value "Hello from inner scope"
		
		// This prints the inner scope message
		fmt.Println(message)
	}
	
	// This prints the outer scope message
	fmt.Println(message)
}