Swift Quick Refresher for iOS

Let's think about this for a moment

Optionals (`?`, `if let`, `guard let`) are used constantly in iOS development — they're crucial for protecting against crashes in scenarios like API responses or user input, where a value 'may or may not' be there. You'll see Closures (`{ ... }`) used for button actions and list transformations. You'll use Structs (`struct Todo { var title: String; var isDone: Bool = false }`) to represent your app's data models (a todo item, a user profile) — even SwiftUI Views are structs (not classes) — that's an intentional design choice for performance.

Let's connect this to a real-world scenario

Writing `var name: String? = nil` tells the compiler that 'name' could be nil — writing `guard let unwrappedName = name else { return }` makes the function early-return if name is nil, protecting against a crash. You'll see button actions written with trailing closure syntax, like `Button("Save") { print("saved") }`, again and again once we get to SwiftUI (next lesson).

• Optionals (?, if let, guard let) = a core Swift feature for protecting against crashes on iOS
• Closures ({ ... }) = used constantly for button actions and list transformations
• Struct = used to represent app data models (like a todo item) — SwiftUI Views are structs too

Let's look at it together

// Optional safety
var name: String? = nil
func greet() {
    guard let unwrappedName = name else {
        print("No name provided")
        return
    }
    print("Hello, \(unwrappedName)!")
}

// Struct — will represent our UI data later
struct TodoItem: Identifiable {
    let id = UUID()
    var title: String
    var isDone: Bool = false
}

$ greet()
No name provided