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Swift Academy · Lesson

Operators: map, filter, combineLatest

Transforming and combining publisher streams with Combine operators.

Operators: map, filter, combineLatest is a free Swift Academy lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

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?

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.

Frequently asked questions

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

Yes — the full text of “Operators: map, filter, combineLatest” is free to read here on the web, and the Swift Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Swift Academy course, upgrade to CoddyKit PRO.

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; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

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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