Swift references M–R

M

Map

Map transforms each element in a collection using a closure.

let numbers = [1, 2, 3]
let doubled = numbers.map { $0 * 2 }

Usage tip: Process data for SwiftUI views in iOS; efficient transformations for watchOS arrays.

Modifier

Modifier customizes SwiftUI views.

Text("Hello").font(.title)

Usage tip: Chain for styling in iOS interfaces; optimize modifiers on watchOS to avoid redraws.

N

NavigationStack

NavigationStack manages a stack of views for navigation in SwiftUI.

NavigationStack {
    NavigationLink("Go", destination: Text("Destination"))
}

Usage tip: Build hierarchical UIs in iOS apps; limited depth on watchOS for usability.

Nil

Nil represents the absence of a value for optionals.

let optional: String? = nil

Usage tip: Handle missing data in iOS models; check for nil in watchOS to prevent errors.

NotificationCenter

NotificationCenter broadcasts information within an app.

NotificationCenter.default.post(name: .init("event"), object: nil)

Usage tip: Sync state across iOS views; use for watchOS complications updates.

O

Observable

Observable is a macro for types that notify changes to observers.

@Observable
class ViewModel {
    var count = 0
}

Usage tip: Reactive state in SwiftUI for iOS; efficient updates on watchOS.

Optional

Optional is a type that can hold a value or nil.

var maybe: Int? = 42

Usage tip: Safe handling in iOS APIs; unwrap carefully on watchOS.

Override

Override reimplements a superclass method.

class Base { func method() {} }
class Derived: Base { override func method() {} }

Usage tip: Customize behavior in iOS subclasses; rarely needed on watchOS.

P

Protocol

Protocol defines a blueprint of methods and properties.

protocol Identifiable {
    var id: Int { get }
}

Usage tip: Conform types for SwiftUI in iOS; protocols for watchOS extensions.

Property Wrapper

Property wrapper adds behavior to properties.

@propertyWrapper struct Clamped<T: Comparable> {
    var wrappedValue: T
}

Usage tip: State management in iOS views; custom wrappers for watchOS.

Published

Published is a property wrapper that publishes changes.

class ViewModel: ObservableObject {
    @Published var count = 0
}

Usage tip: Bind to SwiftUI in iOS; reactive UI on watchOS.

Q

Queue

Queue is a data structure for FIFO operations, often using DispatchQueue.

let queue = DispatchQueue(label: "com.example.queue")
queue.async { print("Task") }

Usage tip: Background work in iOS; concurrent tasks on watchOS.

R

Repeat-While

Repeat-while executes a loop at least once, checking the condition after.

repeat {
    // code
} while condition

Usage tip: Guaranteed execution in iOS loops; useful for watchOS retries.

Return

Return exits a function and provides a value.

func sum(a: Int, b: Int) -> Int {
    return a + b
}

Usage tip: Function results in iOS logic; clear returns on watchOS.

Reduce

Reduce combines collection elements into a single value.

let sum = [1, 2, 3].reduce(0, +)

Usage tip: Aggregate data for iOS stats; computations on watchOS.