Mobile development cheat sheet (iOS)

1. 1Swift essentialsThe Swift 6 that SwiftUI code relies on: optionals, value types, enums, closures, protocols, errors and structured concurrency with actors.11 concepts

   1. 1let, var and type inferencelet declares a constant and var a variable.
   2. 2Optionals and unwrappingAn optional String? either holds a value or nil.
   3. 3Structs versus classesStructs are value types: assigning one makes an independent copy.
   4. 4Enums with associated valuesSwift enums can carry data with each case, such as .loaded([Post]).
   5. 5Closures and capture listsClosures are functions without a name that capture surrounding values.
   6. 6Protocols and extensionsA protocol lists requirements a type promises to meet, like Identifiable or Codable.
   7. 7Error handling with throwsA function marked throws can fail; callers use try inside do and catch.
   8. 8async/await and TaskAn async function can suspend while waiting.
   9. 9Actors, MainActor and SendableAn actor protects its state so only one task touches it at a time.
   10. 10Swift Package ManagerApple's dependency manager, built into Xcode.
   11. 11Swift collectionsArray, Dictionary and Set are value types: assigning one copies it, cheaply, with copy on write.

   11 in this chapterOpen this chapter
2. 2UI and layoutTurning a design into screens: small composable pieces, layout containers, long lists, forms, theming and fitting every screen size.9 concepts

   1. 1Declarative UIYou describe what the screen should look like for the current state, and the framework works out what to change on screen.
   2. 2View modifiersA modifier such as .padding() or .font(.headline) returns a new view that wraps the original.
   3. 3Rows, columns and stacksThe basic layout containers place children horizontally, vertically or on top of each other, with spacing and alignment options.
   4. 4Lazy listsA lazy list only builds the rows currently on screen, plus a few ahead, and recycles them as you scroll.
   5. 5Text input and formsA text field shows a value from state and reports every change back.
   6. 6Theming and dark modeA theme defines colours, typography and shapes in one place.
   7. 7Platform design guidelinesMaterial Design 3 is Google's design system for Android, and the Human Interface Guidelines are Apple's rules for iOS.
   8. 8Safe areas and screen sizesSafe areas, or insets, are the parts of the screen not covered by the notch, status bar, camera cutout or gesture bar.
   9. 9Hot reload and previewsTools that show code changes in a running app or an editor preview within a second or two, without rebuilding the whole app.

   9 in this chapterOpen this chapter
3. State and navigationWhere state lives, how screens share it and how users move between screens, including tabs, sheets and deep links.9 conceptsOpens with credits
4. Networking and local dataCalling APIs, storing data on the device and keeping the app useful on a slow or missing connection, with tokens kept safe.10 conceptsOpens with credits
5. Device features and notificationsWhat makes a phone a phone: the app lifecycle, permissions, camera, location, notifications, background work and calling native code.7 conceptsOpens with credits
6. Testing, performance and accessibilityProving the app works and keeps working: unit and UI tests, profiling a release build, accessibility with real screen readers and a security check.9 conceptsOpens with credits
7. Publishing and releasesGetting the app to real users: IDs and versions, release builds and signing, beta testing, privacy declarations, store review, crash reporting and rollouts.10 conceptsOpens with credits
8. 8Glossary, A to ZEvery concept in the sheet and the smaller terms it uses, in one list.137 terms

Apps for Android and iOS.