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Swift Academy · Lesson

Networking with Combine and URLSession

Using URLSession.dataTaskPublisher with Combine to handle network responses.

Lesson 4 of 412 steps

Networking with Combine and URLSession is a free Swift Academy lesson on CoddyKit. This is lesson 4 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

URLSession has built-in Combine support via `dataTaskPublisher`. Combined with `decode`, it makes type-safe networking pipelines in just a few lines.

dataTaskPublisher

```swift URLSession.shared .dataTaskPublisher(for: URL(string:"https://api.example.com/users")!) .sink(receiveCompletion: { print($0) }, receiveValue: { data, response in print(data.count) }) .store(in: &cancellables) ```

Decoding JSON

```swift struct User: Decodable { var name: String; var id: Int } URLSession.shared .dataTaskPublisher(for: url) .map(\.data) .decode(type: [User].self, decoder: JSONDecoder()) .receive(on: DispatchQueue.main) .sink(receiveCompletion: { print($0) }, receiveValue: { users in self.users = users }) .store(in: &cancellables) ```

Error Handling with catch

```swift .catch { error -> AnyPublisher<[User],Never> in print("Error: \(error)") return Just([]).eraseToAnyPublisher() } ```

retry

```swift .retry(3) // retry up to 3 times on failure ```

Validating HTTP Status

```swift .tryMap { data, response -> Data in guard let http = response as? HTTPURLResponse, (200...299).contains(http.statusCode) else { throw URLError(.badServerResponse) } return data } ```

Building a Generic Publisher

```swift func fetch(_ url: URL) -> AnyPublisher { URLSession.shared.dataTaskPublisher(for: url) .map(\.data) .decode(type: T.self, decoder: JSONDecoder()) .eraseToAnyPublisher() } ```

Cancellation

```swift var searchCancellable: AnyCancellable? searchCancellable?.cancel() // cancel previous searchCancellable = fetch(url).sink { ... } ```

flatMap for Sequential Requests

```swift fetch(userUrl) .flatMap { user in fetch(user.profileUrl) } .sink { profile in render(profile) } .store(in: &cancellables) ```

Combining Multiple Requests

```swift Publishers.Zip(fetch(url1), fetch(url2)) .sink { a, b in combinedUI(a, b) } .store(in: &cancellables) ```

Quick Check

Which Combine operator decodes publisher output into a Decodable type?
Answer it in the interactive lesson

Recap

Key takeaways: • `dataTaskPublisher(for:)` — Combine-based URL fetching • `.map(\.data)` → `.decode(type:decoder:)` for JSON • `.tryMap` validates HTTP status • `.retry(n)` for automatic retries • `.catch { }` provides a fallback publisher Course complete! Next: Swift Structured Concurrency.
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Frequently Asked Questions

Is the “Networking with Combine and URLSession” lesson free?

Yes — any 3 lessons of the Swift Academy learning path, including “Networking with Combine and URLSession”, 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 “Networking with Combine and URLSession”?

Using URLSession.dataTaskPublisher with Combine to handle network responses. 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 4 of 4.

How long does the “Networking with Combine and URLSession” 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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