Swift Basics

What is Swift?

Swift is a programming language created by Apple in 2014. Its main job is to build applications for all of Apple's platforms, from iPhones and Macs to Apple Watches. Think of any app you use on your iPhone—chances are, it was built with Swift.

Swift is a powerful and intuitive programming language developed by Apple for iOS, macOS, watchOS, and tvOS app development.

Before Swift, developers primarily used a language called Objective-C, which was more complex and had roots stretching back to the 1980s. Apple wanted a modern language that was easier to read, safer to write, and faster to run. The result was Swift. It’s designed to be beginner-friendly, with clean syntax that looks a bit like plain English, but it's also powerful enough for professional developers to build complex, high-performance apps.

Setting Up Your Workspace

To start writing Swift code for Apple devices, you'll need an application called Xcode. Xcode is an Integrated Development Environment, or IDE, which is a fancy way of saying it’s a one-stop shop for developers. It bundles everything you need: a text editor for writing code, a compiler to turn your code into a runnable app, and debugging tools to help you fix mistakes.

You can download Xcode for free directly from the Mac App Store. Once it's installed, you can create your first project.

Open Xcode and select "Create a new Xcode project."
Choose the "App" template under the "iOS" tab.
Give your project a name, like "LearningSwift". Make sure the language is set to "Swift" and the interface is "SwiftUI".
Click "Next" and choose a place to save it.

For quick experiments without setting up a full app, you can use a Playground. In Xcode, just go to File > New > Playground. It's a great way to test small snippets of Swift code and see the results instantly.

Storing Information

At its core, programming is about working with data. To do that, we need places to store information. In Swift, we use constants and variables.

constant

noun

A named value that cannot be changed after it is set.

You declare a constant using the let keyword. Think of it as a label for a piece of information that's permanent, like your birthday or the speed of light. Once you set it, you can't change it.

let maxScore = 100
let myName = "Jordan"

If you need to store a value that can change, you use a variable. Variables are declared with the var keyword. A game score, for example, starts at zero and increases as you play. That's a perfect use case for a variable.

var currentScore = 0
// A little later in the game...
currentScore = 50

A good rule of thumb is to always use let unless you specifically know you'll need to change the value later. This makes your code safer and easier to understand.

Basic Data Types

Swift needs to know what kind of data you're storing. Is it a whole number? A number with a decimal? A piece of text? This is where data types come in. Swift is a type-safe language, meaning it catches errors if you try to mix incompatible types, like adding a number to a piece of text.

Here are some of the most common types you'll use.

Data Type	Description	Example
`Int`	Integer, a whole number.	`let score = 10`
`Double`	A number with a fractional component.	`let pi = 3.14159`
`String`	A sequence of characters, or text.	`let message = "Hello!"`
`Bool`	A Boolean value, either `true` or `false`.	`let isGameOver = false`

Swift is smart enough to figure out the data type on its own most of the time. This is called type inference. When you write let year = 2024, Swift automatically knows that year is an Int.

// Swift infers this is an Int
let players = 4

// Swift infers this is a Double
let price = 19.99

// Swift infers this is a String
let appName = "My Awesome App"

// Swift infers this is a Bool
let needsSetup = true

Sometimes, you might want to be explicit about the type. You can do this with a colon after the name.

var currentHealth: Int = 100

This tells Swift, "I'm creating a variable called currentHealth, and it will always store an Int."

Understanding these basic building blocks—variables, constants, and data types—is the first major step in learning to program in Swift.

Let's check your understanding of these fundamental concepts.

Quiz Questions 1/5

What is the primary purpose of the Swift programming language?

Quiz Questions 2/5

In Swift, when should you declare a value using the let keyword instead of var?

You've now got the essentials down. You know what Swift is, how to set up your environment, and how to store basic pieces of information. This foundation is what all of your future Swift programming will be built upon.

Introduction to Swift Programming