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Swift Academy · Lesson

Operators: map, filter, combineLatest

Transforming and combining publisher streams with Combine operators.

Lesson 2 of 412 steps

Operators: map, filter, combineLatest is a free Swift Academy lesson on CoddyKit. This is lesson 2 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, and your progress syncs across the web and the CoddyKit app. The Swift Academy course includes 4 lessons in total.

Welcome

Combine operators transform, filter, and combine publisher streams. They sit between a publisher and subscriber in the pipeline.

map

```swift [1,2,3].publisher .map { $0 * 2 } .sink { print($0) } // 2, 4, 6 ```

filter

```swift (1...10).publisher .filter { $0 % 2 == 0 } .sink { print($0) } // 2,4,6,8,10 ```

compactMap

```swift ["1","two","3"].publisher .compactMap { Int($0) } .sink { print($0) } // 1, 3 ```

combineLatest

```swift let usernamePublisher = usernameField.textPublisher let passwordPublisher = passwordField.textPublisher usernamePublisher .combineLatest(passwordPublisher) .map { !$0.isEmpty && $1.count >= 8 } .assign(to: &loginButton.$isEnabled) ```

merge

```swift merge(upstream1, upstream2) .sink { print($0) } // interleaved values from both ```

zip

```swift zip(publisher1, publisher2) .sink { print($0, $1) } // pairs values one-to-one ```

flatMap

```swift urls.publisher .flatMap { url in URLSession.shared.dataTaskPublisher(for: url).map(\.data) } .sink { data in ... } ```

debounce

```swift searchTextField.textPublisher .debounce(for: 0.3, scheduler: RunLoop.main) .removeDuplicates() .sink { self.search($0) } .store(in: &cancellables) ```

receive(on:)

```swift networkPublisher .receive(on: DispatchQueue.main) .sink { self.updateUI($0) } ```

Quick Check

Which Combine operator emits a value only when all upstream publishers have emitted new values?
Answer it in the interactive lesson

Recap

Key takeaways: • `map`, `filter`, `compactMap` — transform stream elements • `combineLatest` — latest from both; `zip` — paired one-to-one • `flatMap` — flatten async inner publishers • `debounce` — wait for silence before emitting • `receive(on:)` — switch scheduler for UI work Next: Subjects.
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Frequently Asked Questions

Is the “Operators: map, filter, combineLatest” lesson free?

Yes — any 3 lessons of the Swift Academy learning path, including “Operators: map, filter, combineLatest”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Swift Academy course includes 4 lessons in total.

What will I learn in “Operators: map, filter, combineLatest”?

Transforming and combining publisher streams with Combine operators. You practise Swift Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Swift Academy?

No prior experience is required. Swift Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.

How long does the “Operators: map, filter, combineLatest” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Swift Academy lesson?

Yes. Every Swift Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Publishers and Subscribers
  2. Operators: map, filter, combineLatest
  3. PassthroughSubject and CurrentValueSubject
  4. Networking with Combine and URLSession
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