Introduction to Swift 🦅

Discover why Apple created Swift, how it powers iOS, macOS, watchOS, and beyond — and write your very first line of Swift code.

What You'll Learn in This Lesson

• What Swift is and why Apple built it
• The difference between let (constant) and var (variable)
• Swift's type inference and type safety systems
• String interpolation with \(expression)
• How to set up Xcode or an online Swift playground

Note: Swift runs natively on Apple platforms. Our examples simulate Swift logic using JavaScript. For real Swift, download Xcode or use SwiftFiddle.

🎯 Real-World Analogy: If Objective-C is like a classic vintage car — powerful but complex to drive — then Swift is the modern electric car: sleek, fast, safe, and designed for today's world. Apple built Swift in 2014 to make iOS development accessible to everyone.

1️⃣ What is Swift?

Swift is Apple's modern programming language for building apps on iOS, macOS, watchOS, tvOS, and even server-side applications. It was introduced at WWDC 2014 as a replacement for Objective-C, offering cleaner syntax, better safety, and blazing performance. Swift is open source since 2015 and runs on Linux too.

Key features that make Swift special: type safety (catches errors at compile time), optionals (handles missing values safely), protocol-oriented programming, and Automatic Reference Counting (ARC) for memory management.

2️⃣ Your First Swift Program

Every programming journey starts with "Hello, World!" In Swift, it's just one line: print("Hello, World!"). No semicolons needed, no boilerplate — Swift keeps things clean and readable.

Try It: Hello Swift

Write your first Swift-style program with variables, types, and string interpolation

Try it Yourself »

JavaScript

// Your First Swift Program — simulated in JavaScript
console.log("=== Hello, Swift! ===");
console.log();

// In Swift you write:
//   print("Hello, World!")
// Let's simulate Swift's print function
function print(message) {
  console.log(message);
}

print("Hello, World!");
print("Welcome to Swift programming!");
console.log();

// Swift is strongly typed but uses type inference
// let name: String = "Alice"   — explicit type
// let name = "Alice"           — inferred as String

let name = "Al
...

3️⃣ Swift Playground — Arithmetic & Types

Swift supports all standard arithmetic operators and enforces strict type safety. You can't accidentally add an Int to a Double without explicit conversion — this prevents subtle bugs that plague other languages.

Try It: Swift Playground

Explore arithmetic, type safety, and multiline strings

Try it Yourself »

JavaScript

// Swift Playground — Explore Basic Operations
console.log("=== Swift Arithmetic ===");

let a = 42;
let b = 7;
console.log(a + " + " + b + " = " + (a + b));
console.log(a + " - " + b + " = " + (a - b));
console.log(a + " * " + b + " = " + (a * b));
console.log(a + " / " + b + " = " + (a / b));
console.log(a + " % " + b + " = " + (a % b));
console.log();

// Type safety — Swift won't let you mix types
console.log("=== Type Safety ===");
let intVal = 10;
let doubleVal = 3.14;
// In Swift: let res
...

4️⃣ Setting Up Your Environment

You have several options for writing and running Swift code. Xcode is the gold standard for iOS/macOS development, but you can also use the Swift REPL in Terminal or online playgrounds to get started without any installation.

Try It: Setup Guide

See all the ways to set up and run Swift on your machine

Try it Yourself »

JavaScript

// Setting Up Your Swift Environment
console.log("=== How to Run Swift ===");
console.log();

console.log("Option 1: Xcode (macOS only)");
console.log("  1. Download Xcode from the Mac App Store");
console.log("  2. Open Xcode → File → New → Playground");
console.log("  3. Choose 'Blank' template → Create");
console.log("  4. Write code and press ▶️ to run");
console.log();

console.log("Option 2: Swift REPL (Terminal)");
console.log("  1. Open Terminal on macOS");
console.log("  2. Type: swift"
...

⚠️ Common Mistakes

⚠️

Reassigning a let constant — let x = 5; x = 10 will cause a compile error. Use var for values that change.

⚠️

Mixing types without conversion — let sum = 5 + 3.14 won't compile. Use Double(5) + 3.14.

💡

Pro Tip: Prefer let over var whenever possible. Immutable values are safer and help the compiler optimize your code.

📋 Quick Reference — Swift Basics

Concept	Swift Syntax
Constant	let name = "Alice"
Variable	var score = 0
Explicit type	let age: Int = 25
String interpolation	print("Hi, \(name)!")
Print	print("Hello, World!")
Comment	// single line /* multi */

🎉 Lesson Complete!

You've learned what Swift is and written your first program! Next, we'll dive deep into variables and data types.

Introduction to Swift 🦅

What You'll Learn in This Lesson

1️⃣ What is Swift?

2️⃣ Your First Swift Program

Try It: Hello Swift

3️⃣ Swift Playground — Arithmetic & Types

Try It: Swift Playground

4️⃣ Setting Up Your Environment

Try It: Setup Guide

⚠️ Common Mistakes

📋 Quick Reference — Swift Basics

🎉 Lesson Complete!

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