What you learned

Projects 7, 8, and 9 were the first in the series I consider to be “hard”: you had to parse JSON data, you had to create a complex layout for 7 Swifty Words, and you took your first steps towards creating multithreaded code – code that has iOS do more than one thing at a time.

None of those things were easy, but I hope you felt the results were worth the effort. And, as always, don’t worry if you’re not 100% on them just – we’ll be using Codable and GCD more in future projects, so you’ll have ample chance to practice.

• You’ve now met UITabBarController, which is another core iOS component – you see it in the App Store, Music, iBooks, Health, Activity, and more.
• Each item on the tab bar is represented by a UITabBarItem that has a title and icon. If you want to use one of Apple’s icons, it means using Apple’s titles too.
• We used Data to load a URL, with its contentsOf method. That then got fed to JSONDecoder so that we could read it in code.
• We used WKWebView again, this time to show the petition content in the app. This time, though, we wanted to load our own HTML rather than a web site, so we used the loadHTMLString() method.
• Rather than connect lots of actions in Interface Builder, you saw how you could write user interfaces in code. This was particularly helpful for the letter buttons of 7 Swifty Words, because we could use a nested loop.
• In project 8 we used property observers, using didSet. This meant that whenever the score property changed, we automatically updated the scoreLabel to reflect the new score.
• You learned how to execute code on the main thread and on background threads using DispatchQueue, and also met the performSelector(inBackground:) method, which is the easiest way to run one whole method on a background thread.
• Finally, you learned several new methods, not least enumerated() for looping through arrays, joined() for bringing an array into a single value, and replacingOccurrences() to change text inside a string.

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