Game Development with Swift

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

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

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.

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.

As the Apple Swift developer guide states, "memory management just works in Swift." Swift uses a method called Automatic Reference Counting (you will see it referred to as 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.

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.

Given Swift's age, it is certainly more difficult to find answers to common questions through Internet searches. Objective-C has many years' worth of discussion and answers on helpful forums like Stack Overflow. This issue improves every day as the Swift community continues to develop.

Swift projects will run on iOS7 and higher, and OSX 10.9 and higher. Swift is the wrong choice if, in a rare case, you need to target a device running an older operating system.

SpriteKit is Apple's 2D game development framework and your main tool for iOS 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 – we will use it exclusively in our demo game.

We will learn to use SpriteKit to power the mechanics of our game:

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.

It is important to write well-structured code that is easy to re-use 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.

We will learn 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.

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.

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 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.

Creating a game is a memory 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 finish feeling confident in your ability to create games with Swift and bring them to market in the App Store.

Successfully promoting and marketing your game is an important job, but this text focuses on game development mechanics and Swift code. If you are interested in making money from your games, I strongly advise you to research the best ways to promote yourself within the indie gaming community and to start marketing your game well before launch.

We are going to concentrate on iOS. You can use the techniques in this book for game development on OSX too, but you may need to research publishing and environmental differences.

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 game on virtualized iPhones and iPads on your computer.

To install Xcode, search for xcode in the App Store or visit http://developer.apple.com and click on the Xcode icon. Please note the version of Xcode you are installing. At the time of writing, the current version of Xcode is 6.3.2. Swift is continually evolving and each new Xcode release brings syntax changes to Swift. For the best experience with the code in this book, use Xcode 6.3.x (with Swift version 1.2).

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.

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; do not feel pressure to know what each file does yet, but feel free to explore them if you are curious:

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.

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

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

Select the iOS device of your preference 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 6 for the screenshots in this book, so choose iPhone 6 if you want your results to match my images perfectly.

It is time for our first glimpse of SpriteKit in action! Press the gray play arrow (handy run 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 chalky white text: Hello, World. Click around on the gray background.

You will see spinning fighter jets spawning wherever you click:

I may have gone slightly overboard with the jets . . .

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 spawned a sufficient number of jets, you can close the simulator down and return to Xcode. Note: 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.

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, after we clear away the SpriteKit demo and start on our own game.

Make sure you have GameScene.swift open in Xcode.

The GameScene class implements three functions. 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.

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 us 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 towards the start of our journey! Please remove lines from your GameScene.swift file until it looks like the following code:

import SpriteKit

class GameScene: SKScene {
  override func didMoveToView(view: SKView) {
  }
}

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