Lesson 3 • Beginner
Control Flow 🔀
Make decisions with if/else, master Swift's powerful switch statement with pattern matching, and repeat actions with for-in, while, and repeat-while loops.
What You'll Learn in This Lesson
- • Conditionals:
if,else if,else, and the ternary operator - • Swift's
switchwith ranges, tuples, and pattern matching - • Loops:
for-in,while,repeat-while - • Loop control with
breakandcontinue - • Ranges: closed (
1...5) and half-open (1..<5)
1️⃣ Conditionals
Conditionals let your program make decisions. Swift's if statements don't require parentheses around the condition (unlike C/Java), but the braces are always required — even for single-line bodies.
Try It: Conditionals
Use if/else, comparison operators, logical operators, and ternary
// Swift Conditionals — if, else if, else, guard
console.log("=== if / else if / else ===");
let temperature = 28;
console.log("let temperature = " + temperature);
console.log();
if (temperature > 35) {
console.log("🔥 It's extremely hot! Stay hydrated.");
} else if (temperature > 25) {
console.log("☀️ It's a warm day. Perfect for the beach!");
} else if (temperature > 15) {
console.log("🌤️ It's mild. Grab a light jacket.");
} else if (temperature > 5) {
console.log("🧥 It's cold. Wear
...2️⃣ Switch Statements
Swift's switch is far more powerful than in most languages. It supports ranges (0...100), tuples, pattern matching, and where clauses. Unlike C, there's no implicit fallthrough — each case automatically breaks.
Try It: Switch Statements
Pattern matching with ranges, tuples, and multiple values
// Swift's Powerful Switch Statement
console.log("=== Switch Statement ===");
console.log("Swift's switch is MUCH more powerful than other languages!");
console.log();
// Basic switch
let day = "Wednesday";
console.log("let day = \"" + day + "\"");
switch (day) {
case "Monday": case "Tuesday": case "Wednesday": case "Thursday": case "Friday":
console.log("📅 It's a weekday — time to work!");
break;
case "Saturday": case "Sunday":
console.log("🎉 It's the weekend — time to relax!
...3️⃣ Loops
Swift provides for-in for iterating over sequences, while for condition-based loops, and repeat-while (similar to do-while) which always executes at least once. Use stride(from:to:by:) for custom step values.
Try It: Loops
for-in, while, repeat-while, stride, break, and continue
// Swift Loops — for-in, while, repeat-while
console.log("=== for-in Loop ===");
// Looping over a range
console.log("for i in 1...5 {");
for (let i = 1; i <= 5; i++) {
console.log(" " + i + " × " + i + " = " + (i * i));
}
console.log();
// Looping over an array
console.log("for fruit in fruits {");
let fruits = ["Apple", "Banana", "Cherry"];
for (let fruit of fruits) {
console.log(" 🍎 " + fruit);
}
console.log();
// Enumerated (index + value)
console.log("for (index, fruit) in fruits.
...⚠️ Common Mistakes
default case or cover all enum values.== with optionals — Comparing an optional directly works in Swift, but be careful: nil == nil is true.where clauses in switch/for to add conditions: for i in 1...100 where i % 2 == 0.📋 Quick Reference — Control Flow
| Construct | Swift Syntax |
|---|---|
| if/else | if x > 5 { ... } else { ... } |
| switch | switch val { case 1: ... } |
| for-in range | for i in 1...10 { ... } |
| for-in array | for item in array { ... } |
| while | while x > 0 { ... } |
| repeat-while | repeat { ... } while x > 0 |
| stride | stride(from: 0, to: 10, by: 2) |
🎉 Lesson Complete!
You've mastered conditionals, switch statements, and loops! Next, learn about functions and closures.
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