Swift

The powerful programming language that is also easy to learn.

Swift is a powerful and intuitive programming language for macOS, iOS, watchOS, tvOS and beyond. Writing Swift code is interactive and fun, the syntax is concise yet expressive, and Swift includes modern features developers love. Swift code is safe by design, yet also produces software that runs lightning-fast.

    Introducing Swift 5.1

    Swift 5.1 now makes it easier to create and share binary frameworks with others. It also includes features that make it easier to design better APIs and reduce the amount of common boilerplate code.

    Key Features

    • Module stability defines a new text-based module interface file that describes the API of a binary framework.
    • Property wrappers introduce a general purpose syntax for defining custom access patterns for property values.
    • Opaque result types help hide implementation details in APIs.
    • 'Self' can now be used for classes and value types.
    • Support for handling and updating diffs on collections of appropriate types.
    • Improvements to SIMD and String types.

    Modern

    Swift is the result of the latest research on programming languages, combined with decades of experience building Apple platforms. Named parameters are expressed in a clean syntax that makes APIs in Swift even easier to read and maintain. Even better, you don’t even need to type semi-colons. Inferred types make code cleaner and less prone to mistakes, while modules eliminate headers and provide namespaces. To best support international languages and emoji, Strings are Unicode-correct and use a UTF-8 based encoding to optimize performance for a wide-variety of use cases. Memory is managed automatically using tight, deterministic reference counting, keeping memory usage to a minimum without the overhead of garbage collection.

    struct Player {
        var name: String
        var highScore: Int = 0
        var history: [Int] = []
    
        init(_ name: String) {
            self.name = name
        }
    }
    
    var player = Player("Tomas")

    Declare new types with modern, straightforward syntax. Provide default values for instance properties and define custom initializers.

    extension Player {
        mutating func updateScore(_ newScore: Int) {
            history.append(newScore)
            if highScore < newScore {
                print("\(newScore)! A new high score for \(name)! 🎉")
                highScore = newScore
            }
        }
    }
    
    player.updateScore(50)
    // Prints "50! A new high score for Tomas! 🎉"
    // player.highScore == 50

    Add functionality to existing types using extensions, and cut down on boilerplate with custom string interpolations.

    extension Player: Codable, Equatable {}
    
    import Foundation
    let encoder = JSONEncoder()
    try encoder.encode(player)
    
    print(player)
    // Prints "Tomas, games played: 1, high score: 50”

    Quickly extend your custom types to take advantage of powerful language features, such as automatic JSON encoding and decoding.

    let players = getPlayers()
    
    // Sort players, with best high scores first
    let ranked = players.sorted(by: { player1, player2 in
        player1.highScore > player2.highScore
    })
    
    // Create an array with only the players’ names
    let rankedNames = ranked.map { $0.name }
    // ["Erin", "Rosana", "Tomas"]

    Perform powerful custom transformations using streamlined closures.

    These forward-thinking concepts result in a language that is fun and easy to use.

    Swift has many other features to make your code more expressive:

    • Generics that are powerful and simple to use
    • Protocol extensions that make writing generic code even easier
    • First class functions and a lightweight closure syntax
    • Fast and concise iteration over a range or collection
    • Tuples and multiple return values
    • Structs that support methods, extensions, and protocols
    • Enums can have payloads and support pattern matching
    • Functional programming patterns, e.g., map and filter
    • Native error handling using try / catch / throw

    Designed for Safety

    Swift eliminates entire classes of unsafe code. Variables are always initialized before use, arrays and integers are checked for overflow, memory is automatically managed, and enforcement of exclusive access to memory guards against many programming mistakes. Syntax is tuned to make it easy to define your intent — for example, simple three-character keywords define a variable ( var ) or constant ( let ). And Swift heavily leverages value types, especially for commonly used types like Arrays and Dictionaries. This means that when you make a copy of something with that type, you know it won’t be modified elsewhere.

    Another safety feature is that by default Swift objects can never be nil. In fact, the Swift compiler will stop you from trying to make or use a nil object with a compile-time error. This makes writing code much cleaner and safer, and prevents a huge category of runtime crashes in your apps. However, there are cases where nil is valid and appropriate. For these situations Swift has an innovative feature known as optionals. An optional may contain nil, but Swift syntax forces you to safely deal with it using the ? syntax to indicate to the compiler you understand the behavior and will handle it safely.

    extension Collection where Element == Player {
        // Returns the highest score of all the players,
        // or `nil` if the collection is empty.
        func highestScoringPlayer() -> Player? {
            return self.max(by: { $0.highScore < $1.highScore })
        }
    }

    Use optionals when you might have an instance to return from a function, or you might not.

    if let bestPlayer = players.highestScoringPlayer() {
        recordHolder = """
            The record holder is \(bestPlayer.name),\
            with a high score of \(bestPlayer.highScore)!
            """
    } else {
        recordHolder = "No games have been played yet.")
    }
    print(recordHolder)
    // The record holder is Erin, with a high score of 271!
    
    let highestScore = players.highestScoringPlayer()?.highScore ?? 0
    // highestScore == 271

    Features such as optional binding, optional chaining, and nil coalescing let you work safely and efficiently with optional values.

    Fast and Powerful

    From its earliest conception, Swift was built to be fast. Using the incredibly high-performance LLVM compiler technology, Swift code is transformed into optimized native code that gets the most out of modern hardware. The syntax and standard library have also been tuned to make the most obvious way to write your code also perform the best whether it runs in the watch on your wrist or across a cluster of servers.

    Swift is a successor to both the C and Objective-C languages. It includes low-level primitives such as types, flow control, and operators. It also provides object-oriented features such as classes, protocols, and generics, giving Cocoa and Cocoa Touch developers the performance and power they demand.

    Great First Language

    Swift can open doors to the world of coding. In fact, it was designed to be anyone’s first programming language, whether you’re still in school or exploring new career paths. For educators, Apple created free curriculum to teach Swift both in and out of the classroom. First-time coders can download Swift Playgrounds—an app for iPad that makes getting started with Swift code interactive and fun.

    Aspiring app developers can access free courses to learn to build their first apps in Xcode. And Apple Stores around the world host Today at Apple Coding & Apps sessions where you can get hands-on experience with Swift code.

    Learn more about Swift education resources from Apple

    Source and Binary Compatibility

    With Swift 5, you don’t have to modify any of your Swift 4 code to use the new version of the compiler. Instead you can start using the new compiler and migrate at your own pace, taking advantage of new Swift 5 features, one module at a time. And Swift 5 now introduces binary compatibility for apps. That means you no longer need to include Swift libraries in apps that target current and future OS releases, because the Swift libraries will be included in every OS release going forward. Your apps will leverage the latest version of the library in the OS, and your code will continue to run without recompiling. This not only makes developing your app simpler, it also reduces the size of your app and its launch time.

    Open Source

    Swift is developed in the open at Swift.org, with source code, a bug tracker, forums, and regular development builds available for everyone. This broad community of developers, both inside Apple as well as hundreds of outside contributors, work together to make Swift even more amazing. There is an even broader range of blogs, podcasts, conferences and meetups where developers in the community share their experiences of how to realize Swift’s great potential.

    Cross Platform

    Swift already supports all Apple platforms and Linux, with community members actively working to port to even more platforms. With SourceKit-LSP, the community is also working to integrate Swift support into a wide-variety of developer tools. We’re excited to see more ways in which Swift makes software safer and faster, while also making programming more fun.

    Swift for Server

    While Swift powers many new apps on Apple platforms, it’s also being used for a new class of modern server applications. Swift is perfect for use in server apps that need runtime safety, compiled performance and a small memory footprint. To steer the direction of Swift for developing and deploying server applications, the community formed the Swift Server work group. The first product of this effort was SwiftNIO, a cross-platform asynchronous event-driven network application framework for high performance protocol servers and clients. It serves as the foundation for building additional server-oriented tools and technologies, including logging, metrics and database drivers which are all in active development.

    To learn more about the open source Swift community and the Swift Server work group, visit Swift.org

    Playgrounds and Read-Eval-Print-Loop (REPL)

    Much like Swift Playgrounds for iPad, playgrounds in Xcode make writing Swift code incredibly simple and fun. Type a line of code and the result appears immediately. You can then Quick Look the result from the side of your code, or pin that result directly below. The result view can display graphics, lists of results, or graphs of a value over time. You can open the Timeline Assistant to watch a complex view evolve and animate, great for experimenting with new UI code, or to play an animated SpriteKit scene as you code it. When you’ve perfected your code in the playground, simply move that code into your project. Swift is also interactive when you use it in Terminal or within Xcode’s LLDB debugging console. Use Swift syntax to evaluate and interact with your running app, or write new code to see how it works in a script-like environment.

    Package Manager

    Swift Package Manager is a single cross-platform tool for building, running, testing and packaging your Swift libraries and executables. Swift packages are the best way to distribute libraries and source code to the Swift community. Configuration of packages is written in Swift itself, making it easy to configure targets, declare products and manage package dependencies. New to Swift 5, the swift run command now includes the ability to import libraries in a REPL without needing to build an executable. Swift Package Manager itself is actually built with Swift and included in the Swift open source project as a package.

    Objective-C Interoperability

    You can create an entirely new application with Swift today, or begin using Swift code to implement new features and functionality in your app. Swift code co-exists along side your existing Objective-C files in the same project, with full access to your Objective-C API, making it easy to adopt.

    Get Started

    Download Xcode and learn how to build apps using Swift with documentation and sample code.

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