UIKit Development

UIKit Mini Project: Learning Library

Integrate navigation, adaptive collections, forms, diffable state, interoperability, and accessibility in one UIKit feature.

Intermediate6 min read2 guided activities

Before you begin

What you will understand

Plan a UIKit feature around explicit state and routes.
Build a vertical slice from list to detail and editing.
Apply snapshots from stable model identity.
Review lifecycle, accessibility, adaptation, and testability.

Learning stage

Concept Explanation

The mini project is a Learning Library with a searchable course collection, course detail, completion state, and an editor sheet. Build vertical slices: application shell and routes, collection layout and snapshot, detail navigation, editing and validation, then accessibility and adaptation. Keep data in a store and let controllers render state and emit intent.

Use a tab or navigation root, a collection view with compositional layout, stable IDs with a diffable data source, and a coordinator for transitions. The editor owns temporary form input until Save. Add one interoperability boundary—such as a SwiftUI progress summary hosted in UIKit—to practice explicit ownership rather than mixing frameworks everywhere.

Completion means more than a happy-path demo. Verify loading, empty, content, filtered-empty, validation-error, and restored states. Test large text, VoiceOver, right-to-left layout, compact and wide windows, cancellation, repeated presentation, and controller deallocation. Document trade-offs and one next refactoring you would make as the feature grows.

Store: source of truth for courses and progress.
Coordinator: owns construction and navigation.
View controller: renders state and forwards user intent.
Snapshot: identity-driven collection presentation.
Editor draft: temporary values committed only on Save.
Acceptance review: verifies behavior, accessibility, adaptation, and lifecycle.

Learning stage

Syntax & Examples

The coordinator assembles dependencies once and keeps route decisions outside individual screens.

AppCoordinator.swiftswift

@MainActor
final class AppCoordinator {
  private let store: LearningStore
  let rootViewController: UINavigationController

  init(store: LearningStore) {
    self.store = store
    self.rootViewController = UINavigationController()
  }

  func start() {
    let library = LibraryViewController(store: store)
    library.onSelect = { [weak self] id in self?.showCourse(id) }
    library.onCreate = { [weak self] in self?.showEditor() }
    rootViewController.setViewControllers([library], animated: false)
  }

  private func showCourse(_ id: Course.ID) {
    let detail = CourseDetailViewController(courseID: id, store: store)
    rootViewController.pushViewController(detail, animated: true)
  }

  private func showEditor() {
    let editor = CourseEditorViewController()
    editor.onSave = { [weak self, weak editor] draft in
      self?.store.add(draft)
      editor?.dismiss(animated: true)
    }
    rootViewController.present(UINavigationController(rootViewController: editor),
                               animated: true)
  }
}

Screens communicate user intent; the coordinator constructs routes and the store remains the single source of truth.

Learning stage

Real-World Usage

Connect the UIKit concept to complete, maintainable application features.

Create a portfolio project demonstrating modern UIKit practices.
Practice building features that survive changing data and repeated navigation.
Document architecture choices for interviews and code reviews.
Use Instruments, Accessibility Inspector, and tests to turn observations into improvements.

Learning stage

Common Mistakes

Identify lifecycle, ownership, identity, layout, accessibility, and user-experience risks.

Building every screen before one complete flow works.
Letting cells mutate the store directly.
Using index paths as course identity.
Adding accessibility only after visual polish.
Calling the project complete without error, empty, cancellation, and deallocation checks.

Learning stage

Practice Exercises

Build the behavior in a small Xcode project and inspect it across realistic states.

Activity 1

Build the core vertical slice

Implement library list, course detail, completion update, and navigation before adding search or editing.

Hint: Verify that returning to the list reflects completion through a new snapshot.

Activity 2

Run a release-readiness review

Test all named UI states, large text, VoiceOver, RTL, window resizing, keyboard flow, repeated presentations, and deallocation. Record findings and fixes.

Hint: Write acceptance criteria before the review so success is observable.

Learning stage

Knowledge Check

Answer each question before revealing the explanation.

QUESTION 1

Where should durable course and completion state live?

A.In a dedicated store or model layer
B.Only inside visible cells
C.In index paths
D.Inside accessibility labels

Reveal answer

In a dedicated store or model layer

Controllers and cells may be recreated; durable application state needs independent ownership.

QUESTION 2

Why build a vertical slice before every screen?

Reveal answer

It validates architecture, data flow, navigation, and user value end to end while changes remain inexpensive.

A complete narrow path exposes integration problems earlier than disconnected screen shells.

Learning stage

Interview Preparation

Explain the design in terms of lifecycle, identity, ownership, system behavior, and trade-offs.

Walk through the architecture and trade-offs of your UIKit mini project.

Short answer: A store owns data, controllers render state, a coordinator owns routes, and diffable snapshots map stable identity into the collection.

Explore the detailed answer

I would explain boundaries first, then trace selection, editing, save, and UI refresh. I would show how lifecycle and cancellation are handled, why the layout adapts to width, how accessibility is verified, and where UIKit–SwiftUI interoperability has one clear source of truth. Finally I would name limits and the next evidence-driven refactor.

Possible follow-ups

• How would you add persistence?
• Which parts would you unit test versus UI test?

Learning stage

Key Takeaways

The Learning Library integrates UIKit's core systems into a maintainable vertical feature whose state, identity, routes, lifecycle, and accessibility can be explained and tested.

Build vertical slices.
Keep durable state outside controllers and cells.
Route through explicit coordinator decisions.
Drive collections with stable identity.
Treat accessibility, adaptation, failure states, and deallocation as completion criteria.