Due to its close connection with Apple and iOS devices, the Swift programming language is one of today’s most popular languages for iOS developers, software engineers and programming enthusiasts. While Apple has designed Swift to be a relatively easy language to learn, it offers a level of complexity for those who choose to master it.

We’ve written this article to serve as a single touchpoint for initial Swift code development. All of the advice below is designed to help developers using Swift for the first time, as well as experienced developers looking to better understand Swift and its applications. Professionals at a Swift app development company might also find these fundamentals useful when onboarding new team members.

Throughout this article, we’ll outline many of Swift’s key concepts while sharing real-world coding examples. But before we do, it’s worth detailing the best use cases for the following Swift code examples.

What is Swift Used For? A Brief History of the Programming Language and the Best Applications for Swift Code

The Swift programming language was created in 2010 by Chris Lather. From its inception, it was designed to serve as a general-purpose language for Apple devices. Since then, Swift has undergone multiple updates and iterations, the most recent of which was Swift 6.0, released in September 2024.

These are the core use cases for Swift today:

1. iOS and macOS App Development

Since it was first designed, the main use case for Swift has been to build various different applications for Apple devices. That includes apps for iPhones as well as iPads and Macs. Swift is heavily entwined with Mac development to the point where it serves as the default language for developing apps in Xcode.

Some of today’s most popular iPhone apps were built using Swift: Airbnb’s iOS app, as well as LinkedIn, Lyft and many others. If you work in iOS app development, you should know how to code with Swift.

2. watchOS and tvOS Development

Alongside developing apps for Apple’s core devices, Swift is also used to develop apps and solutions for Apple’s further suite of solutions. This includes apps for both Apple Watch and Apple TV. Designing solutions for these apps with Swift allows them to seamlessly integrate with Apple’s wider ecosystem.

3. Server-side Development

One of the core features of Swift is its ability to function cross-platform on both Windows and Linux. This means it’s often used as a server-side language in a variety of use cases, like building high-performance web APIs and backend services. Apple, as well as other major companies like IBM, have used Swift in the past to create scalable web applications.

4. Game Development for Apple Platforms

Swift can also be an option for game developers who are designing games for iOS devices. While it doesn’t offer quite as much flexibility as some more complex coding languages for games, like C/C++, Swift can be used to code casual games for mobile applications.

5. Cross-platform Development

Now that Swift works across both Windows and Linux, it’s also a reliable option for cross-platform development. Developers design applications that can operate across both iOS and Android Linux operating devices or devices that run on Windows. The potential for cross-platform development is further supported by the fact that Swift is still an open-source language, with many developers sharing their expertise.

Swift Code Examples: Understanding the Fundamentals of the Swift Programming Language

Let’s review some of the fundamentals of Swift for anyone just getting started with using the language to write code for iOS apps. 

You first need to understand that Swift is a statically typed and type-safe language. Statically typed means that data types written using Swift are only defined during compile time, and they can’t change during runtime. This makes it slightly harder to use but does mean Swift is more reliable and often performs better than dynamically typed alternatives. Meanwhile, Swift being a type-safe language means you cannot mix different data types in an operation unless explicitly converted. This is designed to avoid type errors.

Basic Swift Code Examples: Variables, Constants and Data Types

When you’re starting out with Swift, understanding variables, constants, and data types is crucial for writing efficient code.

Let’s start with variables and constants. In Swift, you use var to declare mutable (changeable) variables and let to declare immutable (constant) variables. Here’s an example of how these descriptive variable names work in practice:

var name = "Alice"  // A variable (can be changed)
let age = 25        // A constant (cannot be changed)


name = "Bob"   // Allowed, since name is a variable
// age = 30   // Error! 'age' is a constant and cannot be changed

Changeable variables written using var can be changed – in this example, the name in the first line of code is Alice, and it’s possible to change it to Bob. Meanwhile, you can use let to declare immutable variables that can’t change – in this example, the age is set at 25, and when you attempt to change the age to 30, you receive an error. If you wanted to change the age as well as the name in this example, both variables would need to begin with var.

To keep your code clean, it’s worth using the let keyword in your type string by default to declare multiple constants throughout your source code unless you know a variable definitely needs to change.

What about data types? Swift provides programmers with built-in data types, and because it’s type-safe, you can’t mix different data types unless they’ve been explicitly converted. Here’s a quick table showing some of the most common data types in Swift:

Swift allows you to access type inference, which is where Swift designates data types automatically. This can result in cleaner, faster code, but there are cases where it’s better to explicitly type yourself for clarity. Here’s a real-world example of some of these data types being applied within Swift code:

let message: String = "Hello, Swift!"
let pi: Double = 3.14159
let isSwiftAwesome: Bool = true
let numbers: [Int] = [1, 2, 3, 4, 5]
let user: [String: Any] = ["name": "Alice", "age": 25]

As you can see in this example, each data type has been made a constant because they start with a let keyword. 

Understanding each of these data types, as well as applying variables and constants, is one of the core fundamentals of effective Swift coding. Once you better understand them, you can move on to how Swift handles control flow.

Basic Swift Code Examples: Control Statements

Swift uses control flow statements for program execution, much like many programming languages. The most common of these are if and else statements, as well as switches and loops including for, while, and repeat-while.

Here’s a quick summary of each of these statements and their purpose during code execution, such as statements that work off of Boolean conditions: 

These are fairly basic examples of control statements within Swift, and if you’re familiar with programming you should understand how they work already. There are, however, some more advanced control statements you can use to create more dynamic code.

One example of this is using the where clause to filter values while iterating over a sequence. Here’s one of our real-world Swift code examples showing how this works in a case where you need to filter even numbers:

for number in 1...10 where number % 2 == 0 {
    print("\(number) is even")
}
// Output:
// 2 is even
// 4 is even
// 6 is even
// 8 is even
// 10 is even

Another more advanced control statement targeting loops is the process of breaking out of loops early once a certain condition has been met. Here’s an example where the break statement is used to break a loop once a specific value has been found:

let numbers = [3, 7, 15, 22, 30]
for num in numbers {
    print("Checking \(num)...")
    if num > 20 {
        print("Found a number greater than 20! Stopping.")
        break
    }
}

// Output:
// Checking 3...
// Checking 7...
// Checking 15...
// Checking 22...
// Found a number greater than 20! Stopping.

Further to these techniques, you can also create more advanced switch statements and nest loops within each other when handling multi-dimensional data. Experiment with different control statements to make your code more efficient.

Basic Swift Code Examples: Functions and Closures

The final basic Swift coding fundamentals you need to understand when starting out are both functions and closures. 

Functions are named blocks of Swift code that perform specific tasks. You can apply input parameters to your functions to make them more dynamic, and they can also return values. Here’s an example of a basic function in Swift:

func sayHello() {
    print("Hello, Swift!")
}
sayHello()  // Output: Hello, Swift!

Now, here’s an example featuring input parameters:

func greet(name: String) {

    print("Hello, \(name)!