Summary: Structs

Paul Hudson @twostraws November 8th 2021

Updated for Xcode 13.2

Structs are used almost everywhere in Swift: String, Int, Double, Array and even Bool are all implemented as structs, and now you can recognize that a function such as isMultiple(of:) is really a method belonging to Int.

Let’s recap what else we learned:

You can create your own structs by writing struct, giving it a name, then placing the struct’s code inside braces.
Structs can have variable and constants (known as properties) and functions (known as methods)
If a method tries to modify properties of its struct, you must mark it as mutating.
You can store properties in memory, or create computed properties that calculate a value every time they are accessed.
We can attach didSet and willSet property observers to properties inside a struct, which is helpful when we need to be sure that some code is always executed when the property changes.
Initializers are a bit like specialized functions, and Swift generates one for all structs using their property names.
You can create your own custom initializers if you want, but you must always make sure all properties in your struct have a value by the time the initializer finishes, and before you call any other methods.
We can use access to mark any properties and methods as being available or unavailable externally, as needed.
It’s possible to attach a property or methods directly to a struct, so you can use them without creating an instance of the struct.

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