DAY 10

Structs, part one

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I know some of you might be keen to charge on with today’s new Swift learning, but hold up: you just finished learning about closures, which are a difficult topic. And you came back for more. Seriously, that deserves a lot of respect.

And I have some good news for you. First, not only can you avoid thinking about closures for the next few days, but once you’ve had a break we’ll start putting them into practice in real iOS projects. So, even if you aren’t 100% sure of how they work or why they are needed, it will all become clear – stick with it!

Anyway, today’s topic is structs. Structs are one of the ways Swift lets us create our own data types out of several small types. For example, you might put three strings and a Boolean together and say that represents a user in your app. In fact, most of Swift’s own types are implemented as structs, including String, Int, Bool, Array, and more.

These custom types – users, games, documents, and more – form the real core of the software we build. If you get those right then often your code will follow.

As Fred Brooks, the author of the hugely influential book The Mythical Man-Month, once said, “the programmer at wit’s end... can often do best by disentangling themself from their code, rearing back, and contemplating their data. Representation is the essence of programming.”

What’s more, structs are extremely common in SwiftUI, because every piece of UI we design is built on a struct, with lots of structs inside. They aren’t difficult to learn, but to be fair after closures almost everything seems easier!

Today you have four tutorials to follow, where you’ll meet custom structs, computed properties, property observers, and more. Once you’ve watched each video and optionally gone through the extra reading, there are short tests to help make sure you’ve understood what was taught.

1. How to create your own structs
   • Optional: What’s the difference between a struct and a tuple?
   • Optional: What’s the difference between a function and a method?
   • Optional: Why do we need to mark some methods as mutating?
   • Test: Structs
   • Test: Mutating methods
2. How to compute property values dynamically
   • Optional: When should you use a computed property or a stored property?
   • Test: Computed properties
3. How to take action when a property changes
   • Optional: When should you use property observers?
   • Optional: When should you use willSet rather than didSet?
   • Test: Property observers
4. How to create custom initializers
   • Optional: How do Swift’s memberwise initializers work?
   • Optional: When would you use self in a method?
   • Test: Initializers
   • Test: Referring to the current instance

How can this day be improved?

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