Lesson 12Control Flow

If-Else

Two Paths: If-Else

Sometimes you want to do one thing if a condition is true, and something else if it's false. That's where else comes in!

Basic Syntax

if condition {
    // runs if true
} else {
    // runs if false
}

How It Works

✓

Condition is TRUE

Code inside if block runs

✗

Condition is FALSE

Code inside else block runs

Real-World Examples

🎮

If lives > 0, keep playing. Else, game over!

🔐

If password correct, login. Else, show error!

☀️

If sunny, go outside. Else, stay inside!

Key Points

Only ONE block runs - never both!
The else block is optional
Use curly braces { } for each block

main.swift

// Basic if-else
let age = 15

if age >= 18 {
    print("You are an adult")
} else {
    print("You are a minor")
}

// Checking a boolean
let isLoggedIn = false

if isLoggedIn {
    print("Welcome back!")
} else {
    print("Please log in")
}

// Number comparison
let score = 45

if score >= 60 {
    print("You passed!")
} else {
    print("Keep practicing!")
}

// String comparison
let password = "secret123"
let userInput = "secret123"

if password == userInput {
    print("Access granted!")
} else {
    print("Wrong password!")
}

// Checking if number is even or odd
let number = 7

if number % 2 == 0 {
    print("\(number) is even")
} else {
    print("\(number) is odd")
}

// Real game example
var lives = 0

if lives > 0 {
    print("Keep playing!")
} else {
    print("Game Over!")
}

Try It Yourself!

Write an if-else statement that checks if a number is positive or negative and prints the appropriate message!