Swift Game Development - Third Edition

By Siddharth Shekar , Stephen Haney
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    Designing Games with Swift
About this book
Swift is the perfect choice for game development. Developers are intrigued by Swift and want to make use of new features to develop their best games yet. Packed with best practices and easy-to-use examples, this book leads you step by step through the development of your first Swift game. The book starts by introducing Swift's best features – including its new ones for game development. Using SpriteKit, you will learn how to animate sprites and textures. Along the way, you will master physics, animations, and collision effects and how to build the UI aspects of a game. You will then work on creating a 3D game using the SceneKit framework. Further, we will look at how to add monetization and integrate Game Center. With iOS 12, we see the introduction of ARKit 2.0. This new version allows us to integrate shared experiences such as multiplayer augmented reality and persistent AR that is tied to a specific location so that the same information can be replicated on all connected devices. In the next section, we will dive into creating Augmented Reality games using SpriteKit and SceneKit. Then, finally, we will see how to create a Multipeer AR project to connect two devices, and send and receive data back and forth between those devices in real time. By the end of this book, you will be able to create your own iOS games using Swift and publish them on the iOS App Store.
Publication date:
September 2018


Chapter 1. Designing Games with Swift

Apple's newest version of its flagship programming language, Swift 4.2, is the perfect choice for game developers. As it matures, Swift is realizing its potential to be something special, a revolutionary tool for app creators. Swift is the gateway for developers to create the next big game in the Apple ecosystem. We have only started to explore the wonderful potential of mobile gaming, and Swift is the modernization we need for our toolset. Swift is fast, safe, current, and attractive to developers coming from other languages. Whether you are new to the Apple world, or a seasoned veteran of Objective-C, I think you will enjoy making games with Swift.

Apple's website states the following:

"Swift is a successor to the C and Objective-C languages."

My goal in this book is to guide you step by step through the creation of a 2D and a 3D game for iPhones and iPads. We will start with installing the necessary software, working through each layer of game development, ultimately publishing our new game to the App Store.

We will also have some fun along the way! For the 2D game, we aim to create an endless flyer game featuring a magnificent flying penguin named Pierre. What is an endless flyer? Picture hit games such as iCopter, Flappy Bird, Whale Trail, Jetpack Joyride, and many more—the list is quite long.

Endless flyer games are popular on the App Store, and the genre necessitates that we cover many reusable components of 2D game design. I will show you how to modify our mechanics to create many different game styles.

For the 3D game, we will be using SceneKit. Like SpriteKit, which is used to develop 2D games, SceneKit is a framework developed by Apple to make 3D games. The 3D game we will be an obstacle avoidance game, in which there will be obstacles players will have to either go under or jump over.

In later chapters, we will see how to make augmented reality games using Apple's newest framework, ARKit. With ARKit, you can make really stunning augmented reality games. We will see see how to develop AR games using SpriteKit and SceneKit. Along with developing a 2D AR game, we will also see how to bring the SceneKit game we developed for 3D to life using the ARKit. In addition, we will also see how to create a Multipeer Augemented Reality App using ARKit and Multipeer Connectivity framework.

My hope is that our demo project will serve as a template for your own creative tasks. Before you know it, you will be publishing your own game ideas using the techniques we explore together.

In this chapter, we will cover the following topics:

  • Why you will love Swift

  • What you will learn in this book

  • New in Swift 4.2

  • Setting up your development environment

  • Creating your first Swift game

  • Exploring the SpriteKit demo


Why you will love Swift

Swift, as a modern programming language, benefits from the collective experience of the programming community; it combines the best parts of other languages and avoids poor design decisions. Here are a few of my favorite Swift features:

  • Beautiful syntax: Swift's syntax is modern and approachable, regardless of your existing programming experience. Apple have balanced syntax with structure to make Swift concise and readable.

  • Interoperability: Swift can plug directly into your existing projects and run side by side with your Objective-C code.

  • Strong typing: Swift is a strongly typed language. This means the compiler will catch more bugs at compile time, instead of when your users are playing your game! The compiler will expect your variables to be of a certain type (int, string, and so on) and will throw a compile-time error if you try to assign a value of a different type. While this may seem rigid if you are coming from a weakly typed language, the added structure results in safer, more reliable code.

  • Smart type inference: To make things easier, type inference will automatically detect the types of your variables and constants based upon their initial value. You do not need to explicitly declare a type for your variables. Swift is smart enough to infer variable types in most expressions.

  • Automatic memory management: As the Apple Swift developer guide states, "memory management just works in Swift". Swift uses a method called Automatic Reference Counting (ARC) to manage your game's memory usage. Besides a few edge cases, you can rely on Swift to safely clean up and turn off the lights.

  • An even playing field: One of my favorite things about Swift is how quickly the language is gaining mainstream adoption. We are all learning and growing together, and there is a tremendous opportunity to break new ground.

  • Open source: From version 2.2 onwards, Apple made Swift open source, curating it through the website www.swift.org, and launched a package manager with Swift 3. This is a welcome change, as it fosters greater community involvement and a larger ecosystem of third-party tools and add-ons. Eventually, we should see Swift migrate to new platforms.



I will try to make this text easy to understand for all skill levels:

  • I will assume you are brand new to Swift as a language

  • This book requires no prior game development experience, though any experience you have will help

  • I will assume you have a fundamental understanding of common programming concepts


What you will learn in this book

By the end of this book, you will be capable of creating and publishing your own iOS games. You will know how to combine the techniques we will learn to create your own style of game and you will be well prepared to dive into more advanced topics with a solid foundation in 2D, 3D, and AR game design.

Embracing SpriteKit

SpriteKit is Apple's 2D game development framework and your main tool for iOS, macOS, tvOS, and watchOS game design. SpriteKit will handle the mechanics of our graphics rendering, physics, and sound playback. As far as game development frameworks go, SpriteKit is a terrific choice. It is built and supported by Apple and thus integrates perfectly with Xcode and iOS. You will learn to be highly proficient with SpriteKit as we will be using it exclusively in our demo game.

We will learn how to use SpriteKit to power the mechanics of our game in the following ways:

  • Animating our player, enemies, and power-ups

  • Painting and moving side-scrolling environments

  • Playing sounds and music

  • Applying physics such as gravity and impulses for movement

  • Handling collisions between game objects

Similar to SpriteKit, we will also look at SceneKit. In SceneKit, instead of importing images, we will be loading 3D models, placing them in the scene and creating a game around them. We will also see how to add player movement, animation, physics, controls, collision, and scoring.

In ARKit, with 2D and 3D game demos, we will see how to take existing games and make augmented reality games out of them.

Reacting to player input

The control schemes in mobile games must be inventive. Mobile hardware forces us to simulate traditional controller inputs, such as directional pads and multiple buttons, on the screen. This takes up valuable visible area and provides less precision and feedback than with physical devices. Many games operate with only a single input method: a single tap anywhere on the screen. We will learn how to make the best of mobile input and explore new forms of control by sensing device motion and tilt.

Structuring your game code

It is important to write well-structured code that is easy to reuse and modify as your game design inevitably changes. You will often find mechanical improvements as you develop and test your games, and you will thank yourself for a clean working environment. Though there are many ways to approach this topic, we will explore some best practices to build an organized system with classes, protocols, inheritance, and composition.

Building UI/menus/levels

We will learn how to switch between scenes in our game with a menu screen. We will cover the basics of user experience design and menu layout as we build our demo game.

Integrating with Game Center

Game Center is Apple's built-in social gaming network. Your game can tie into Game Center to store and share high scores and achievements. We will learn how to register for Game Center, tie it into our code, and create a fun achievement system.

Maximizing fun

If you are like me, you will have dozens of ideas for games floating around your head. Ideas come easily, but designing fun gameplay is difficult! It is common to find that your ideas need gameplay enhancements once you see your design in action. We will look at how to avoid dead ends and see your project through to the finish line. Plus, I will share my tips and tricks to ensure your game will bring joy to your players.

Crossing the finish line

Creating a game is an experience you will treasure. Sharing your hard work will only sweeten the satisfaction. Once our game is polished and ready for public consumption, we will navigate the App Store submission process together. You will end up feeling confident in your ability to create games with Swift and bring them to the market in the App Store.

Monetizing your work

Game development is a fun and rewarding process, even without compensation, but the potential exists to start a career, or side job, selling games on the App Store. Successfully promoting and marketing your game is an important task. I will outline your options and start you down the path to monetization.


New in Swift 4.2

This year, we have the release of Swift version 4.2 with Xcode 10. Unlike previous years where we saw a full release of a Swift version, like Swift 3.0 and Swift 4.0, this year, we see the release of Version 4.2. Swift 5.0 has been moved to the sometime early next year in 2019.

Xcode 10 will be the last version to support Swift 3.0 Compatibility Mode. So, if your app uses Xcode version 3, the code needs to be migrated to at least 4.0 by next year.

Further refinements have also been introduced by Apple in Swift 4.2:

  • Speedup Debug Builds: Code builds at least twice as fast compared to previous versions of Xcode. This will depend on the nature of the product and how much Swift code it uses. Compilation is optimized to reduce redundant work.

  • Runtime Optimization: Swift 4.2 introduces a couple of under the hood runtime optimizations. For example, in 4.2, all intermediate retains and releases of objects are removed and the object only gets released once at the end, improving the runtime of the code. This also enables automatic code size optimization.

  • Small String: String is now 16 bites as compared to 24 in the previous version. It also enables a small string memory optimization. If the string is within 15 bites, then the string is represented in the string type without requiring separate allocation to represent the string.

  • Reduction in Code Size: There is a new optimization level which reduces the machine level code size generated from the compilation of the swift code. This optimization enables 10% to 30% reduction in code size with a 5% hit in runtime performance.

Swift has already made tremendous steps forward as a powerful, young language. Now, Apple is working on polishing Swift into a mature, production-ready tool. The overall developer experience improves with Swift 4.2.

With Swift 4.2, we are moving toward binary compatibility and with Swift 5.0 releasing in early 2019, this transition will be complete. With this, Apple will be able to ship the Swift runtime along with the OS itself and doesn't need to be included in the App bundle as it is currently. This will improve startup time and memory usage of the application itself. More information about binary compatibility/ abi-stability is available at swift.org/abi-stability.


For a detailed look at what's new in Swift, I highly recommend watching the WWDC 2018 video:



Setting up your development environment

Learning a new development environment can be a roadblock. Luckily, Apple provides some excellent tools for iOS developers. We will start our journey by installing Xcode.

Introducing and installing Xcode

Xcode is Apple's integrated development environment (IDE). You will need Xcode to create your game projects, write and debug your code, and build your project for the App Store. Xcode also comes bundled with an iOS simulator to test your games on virtualized iPhones and iPads on your computer.

Apple praises Xcode as "an incredibly productive environment for building amazing apps for Mac, iPhone, and iPad".

To install Xcode, search for Xcode in the App Store, or visit http://developer.apple.com, select Developer, and then Xcode.

Swift is continually evolving and each new Xcode release brings changes to Swift. If you run into errors because Swift has changed, you can always use Xcode's built-in syntax update tool. Simply use Xcode's Edit | Convert to Latest Syntax option to update your code.

Xcode performs common IDE features to help you write better, faster code. If you have used IDEs in the past, then you are probably familiar with auto completion, live error highlighting, running and debugging a project, and using a project manager pane to create and organize your files. However, any new program can seem overwhelming at first. We will walk through some common interface functions over the next few pages. I have also found tutorial videos on YouTube to be particularly helpful if you are stuck. Most common search queries result in helpful videos.

Creating our first Swift game

Do you have Xcode installed? Let's see some game code in action in the simulator!

We will start by creating a new project in Xcode. For our demo game, we will create a side-scrolling endless flyer featuring an astonishing flying penguin named Pierre. I am going to name this project Pierre Penguin Escapes the Antarctic, but feel free to name your project whatever you like. Follow these steps to create a new project in Xcode:

  1. Launch Xcode and select Create a new Xcode project:

  2. You will see a screen asking you to select a template for your new project. Select iOS and Game in the pane. It should look like this:

  3. Once you have selected Game, click Next. The following screen asks us to enter some basic information about our project. Don't worry; we are almost at the fun bit. Fill in the Product Name field with the name of your game:

  4. Let's fill in the Team field. Do you have an active Apple Developer account? If not, you can skip over the Team field for now. If you do, your Team is your Developer account. Click Add Team and Xcode will open the Accounts screen, where you can log in. Enter your Developer credentials, as shown in the following screenshot:

  5. Once you're authenticated, you can close the Accounts screen. Your Developer account should appear in the Team dropdown.

  6. You will want to pick a meaningful Organization Name and Organization Identifier when you create your own games for publication. Your Organization Name is the name of your game development studio. For me, that is Joyful Games. By convention, your Organization Identifier should follow a reverse domain name style. I will use com.growlgamesstudio since my website is growlgamesstudio.com.

  7. After you have filled out the name fields, be sure to select Swift for Language, SpriteKit for Game Technology, and Universal for Devices.

  8. For now, uncheck Integrate GameplayKit, uncheck Include Unit Tests, and uncheck Include UI Tests. We will not use these features in our demo game. Here are my final project settings:

  9. Click Next and you will see the final dialog box. Save your new project. Pick a location on your computer and click Next. And we are in! Xcode has pre-populated our project with a basic SpriteKit template.

Navigating our project

Now that we have created our project, you will see the project navigator on the left-hand side of Xcode. You will use the project navigator to add, remove, and rename files and generally organize your project. You might notice that Xcode has created quite a few files in our new project. We will take it slow; don't feel that you have to know what each file does yet, but feel free to explore them if you are curious:


Exploring the SpriteKit demo

Use the project navigator to open up the file named GameScene.swift. Xcode created GameScene.swift to store the default scene of our new game.

What is a scene? SpriteKit uses the concept of scenes to encapsulate each unique area of a game. Think of the scenes in a movie; we will create a scene for the main menu, a scene for the Game Over screen, a scene for each level in our game, and so on. If you are on the main menu of a game and you tap Play, you move from the menu scene to the Level 1 scene.

SpriteKit prepends its class names with the letters "SK"; consequently, the scene class is SKScene.

You will see that there is already some code in this scene. The SpriteKit project template comes with a very short demo. Let's take a quick look at this demo code and use it to test the iOS simulator.

Please do not be concerned with understanding the demo code at this point. Your focus should be on learning about the development environment.

Look for the run toolbar at the top of the Xcode window. It should look something like the following:

Select the iOS device of your choice to simulate using the dropdown on the far right. Which iOS device should you simulate? You are free to use the device of your choice. I will be using an iPhone X for the screenshots in this book, so choose iPhone X if you want your results to match my images perfectly.

Unfortunately, expect your game to play poorly in the simulator. SpriteKit suffers from poor FPS (Frames Per Second) in the iOS simulator. Once our game becomes relatively complex, we will see our FPS drop, even on high-end computers. The simulator will get you through, but it is best if you can plug in a physical device for testing.

It is time for our first glimpse of SpriteKit in action! Press the gray play arrow on the toolbar (handy keyboard shortcut: command + R). Xcode will build the project and launch the simulator. The simulator starts in a new window, so make sure you bring it to the front. You should see a gray background with white text: Hello, World. Click around on the gray background. You will see colorful, spinning boxes spawning wherever you click:

If you have made it this far, congratulations! You have successfully installed and configured everything you need to make your first Swift game.

Once you have finished playing with the spinning squares, you can close the simulator down and return to Xcode. Note that you can use the keyboard command command + Q to exit the simulator, or press the stop button inside Xcode. If you use the stop button, the simulator will remain open and launch your next build faster.


Examining the demo code

Let's quickly explore the demo code. Do not worry about understanding everything just yet; we will cover each element in depth later. At this point, I am hoping you will acclimatize to the development environment and pick up a few things along the way. If you are stuck, keep going! Things will actually get simpler in the next chapter, once we clear away the SpriteKit demo and start on our own game.

Make sure you have GameScene.swift open in Xcode.

The demo GameScene class implements some functions you will use in your games. Let's examine these functions. Feel free to read the code inside each function, but I do not expect you to understand the specific code just yet:

  • The game invokes the didMove function whenever it switches to the GameScene. You can think of it a bit like an initialize, or main, function for the scene. The SpriteKit demo uses it to draw the Hello, World text to the screen and set up the spinning square shape that shows up when we tap.

  • There are seven functions involving touch, which handle the user's touch input to the iOS device screen. The SpriteKit demo uses these functions to spawn the spinning square wherever we touch the screen. Do not worry about understanding these functions at this time.

  • The update function runs once for every frame drawn to the screen. The SpriteKit demo does not use this function, but we may have reason to implement it later.


Cleaning up

I hope that you have absorbed some Swift syntax and gained an overview of Swift and SpriteKit. It is time to make room for our own game; let's clear all of that demo code out! We want to keep a little bit of the boilerplate, but we can delete most of what is inside the functions. To be clear, I do not expect you to understand this code yet. This is simply a necessary step toward the start of our journey.

Firstly, we will remove the Hello, World text from the demo. Open the GameScene.sks file from the project navigator in Xcode. You will see a gray layout view with Hello, World written in the middle. Simply click anywhere on the Hello, World text and press your Delete key to remove it. Make sure you save your file before moving on.

Secondly, please replace all of the code from your GameScene.swift file with the following code:

import SpriteKit

class GameScene: SKScene { 
    override func didMove(to view: SKView) { 

Once your GameScene.swift file looks like the preceding code, you are ready to move on to Chapter 2, Sprites, Camera, Actions! The real fun begins now!



You have already accomplished a lot. You have had your first experience with Swift, installed and configured your development environment, launched code successfully into the iOS simulator, and prepared your project for the first steps toward your own game. Great work!

We have seen enough of the "Hello World" demo; are you ready to draw your own graphics to the game screen? We will make use of sprites, textures, colors, and animation in Chapter 2, Sprites, Camera, Action!

About the Authors
  • Siddharth Shekar

    Siddharth Shekar is a game developer and teacher with over 6 years' industry experience and 12 years' experience in C++ and other programming languages. He is adept at graphics libraries such as OpenGL and Vulkan, and game engines such as Unity and Unreal. He has published games on the iOS and Android app stores. He has also authored books including Swift Game Development, Mastering Android Game Development with Unity, and Learning iOS 8 Game Development Using Swift, all published by Packt Publishing. He currently lives in Auckland, New Zealand, and is a lecturer in the games department at Media Design School. He teaches advanced computer graphics programming, PlayStation 4 native game development, and mentors final year production students.

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  • Stephen Haney

    Stephen Haney has written two books on iOS game development. He began his programming journey at the age of 8 years on a dusty, ancient laptop using BASIC. He has been fascinated with building software and games ever since. Now well versed in multiple languages, he enjoys programming as a creative outlet the most. He believes that indie game development is an art forman amazing combination of visual, auditory, and psychological challengesrewarding to both the player and the creator. He enjoyed writing this book and sincerely hopes that it directly furthers your career or hobby.

    Browse publications by this author
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