What is Swift? Syntax, Usage, and Examples
Swift is a modern, high-performance programming language developed by Apple for building apps across iOS, macOS, watchOS, and tvOS. It combines speed, safety, and ease of use, making it a great choice for beginners and professionals alike.
How to Use Swift
Swift uses a clean and expressive syntax, making it easy to write and read. Here’s a basic Swift program:
swift
print("Hello, Swift!")
This prints “Hello, Swift!” to the console.
Declaring Variables and Constants
Swift distinguishes between variables and constants. Use var for values that change and let for constants.
swift
var userName = "Alice" // Variable (modifiable)
let birthYear = 1990 // Constant (cannot change)
Using constants wherever possible makes code safer and prevents unintended changes.
Data Types and Type Inference
Swift uses type inference, meaning it can automatically determine a variable’s type. You can also specify types explicitly:
swift
var age: Int = 30
var price: Double = 9.99
var isActive: Bool = true
var greeting: String = "Hello"
Explicit typing improves readability and reduces unexpected behavior.
Functions in Swift
Functions encapsulate reusable logic. Define a function using the func keyword:
swift
func greet(name: String) -> String {
return "Hello, \(name)!"
}
print(greet(name: "Alice")) // Output: Hello, Alice!
Functions can take multiple parameters and return values of any type.
Control Flow Statements
Swift provides standard control flow structures like if, switch, and loops.
swift
let temperature = 25
if temperature > 30 {
print("It's hot outside.")
} else if temperature > 20 {
print("It's warm.") // This line executes
} else {
print("It's cold.")
}
Loops allow you to iterate over data.
swift
for number in 1...5 {
print(number) // Prints 1 to 5
}
var count = 3
while count > 0 {
print("Countdown: \(count)")
count -= 1
}
Use loops when you need to execute a block of code multiple times.
When to Use Swift
iOS and macOS Development
Swift is Apple’s primary language for iOS and macOS apps. It integrates seamlessly with Apple’s frameworks like UIKit and SwiftUI.
swift
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
print("Welcome to my app")
}
}
If you’re building an app for an Apple device, Swift is the best choice.
Server-Side Development
Swift can also power backend applications using frameworks like Vapor.
swift
import Vapor
let app = Application()
app.get("hello") { req in
return "Hello, Swift Server!"
}
try app.run()
This makes Swift a full-stack language.
Scripting and Automation
Swift can run scripts directly from the terminal, making it useful for automation.
swift
#!/usr/bin/swift
print("Swift script running")
You can write Swift scripts to handle repetitive tasks efficiently.
Examples of Swift in Action
Using Optionals
Swift’s optionals help prevent crashes by handling missing values safely.
swift
var username: String? = nil
if let user = username {
print("Welcome, \(user)")
} else {
print("No user found") // This line executes
}
Use if let or guard let to safely unwrap optionals.
Structs and Classes
Swift supports both structs and classes for defining custom types.
swift
struct Car {
var brand: String
var speed: Int
func description() -> String {
return "\(brand) is going \(speed) km/h"
}
}
let myCar = Car(brand: "Tesla", speed: 120)
print(myCar.description())
Classes allow inheritance, while structs are value types.
swift
class Animal {
var name: String
init(name: String) {
self.name = name
}
func makeSound() {
print("Some generic sound")
}
}
class Dog: Animal {
override func makeSound() {
print("Woof!")
}
}
let myDog = Dog(name: "Buddy")
myDog.makeSound() // Output: Woof!
Choose structs when working with simple data models and classes for more complex behaviors.
Error Handling
Swift has built-in error handling using do-catch.
swift
enum FileError: Error {
case notFound
case noPermission
}
func readFile(name: String) throws {
throw FileError.notFound
}
do {
try readFile(name: "data.txt")
} catch {
print("Error reading file: \(error)")
}
Use error handling to prevent runtime crashes.
Learn More About Swift
What is Swift Used for in Programming?
Swift is used in:
- iOS and macOS development – The primary language for native Apple apps.
- Server-side applications – Works with frameworks like Vapor.
- Machine learning and AI – Compatible with Core ML and TensorFlow Swift.
- Scripting and automation – Useful for writing system scripts.
Swift vs Objective-C
Swift replaced Objective-C as Apple’s preferred language due to:
- Better performance – Faster execution and memory efficiency.
- Safer syntax – Reduces crashes with optionals and strong typing.
- Modern features – Includes generics, functional programming, and type inference.
If you’re working with Apple’s ecosystem, Swift is the best choice for new projects.
Swift Playgrounds
Swift Playgrounds provides an interactive way to learn Swift without setting up a full project. It’s great for experimenting with Swift code.
Swift is a versatile, fast, and beginner-friendly language. Whether you’re building mobile apps, backend services, or scripts, it offers a clean and efficient coding experience.
If you’re ready to start coding in Swift, check out our Swift Programming course to get hands-on experience with real-world projects.