RxSwift vs Combine: Which Reactive Framework is Best for iOS Development?

 

Reactive programming has become an essential part of modern iOS development. Instead of manually managing callbacks and delegation patterns, reactive frameworks allow developers to handle asynchronous data streams elegantly.

When it comes to iOS, two major players stand out: RxSwift and Combine. Both frameworks let us work with reactive streams, but they have different histories, ecosystems, and trade-offs.

In this post, we’ll compare RxSwift vs Combine, explore their strengths and weaknesses, and walk through a simple example to help you decide which is best for your project.

🔹 What is RxSwift?

RxSwift is the Swift implementation of ReactiveX (Rx) — a cross-platform reactive programming library. It has been around for years, well before Apple introduced Combine.

• Open-source and widely adopted in the iOS community.
• Large ecosystem with operators, community support, and third-party libraries.
• Works on iOS versions earlier than iOS 13.

🔹 What is Combine?

Combine is Apple’s native reactive framework, introduced in WWDC 2019.

• Built directly into the Apple ecosystem.
• Optimized for Swift and integrated with system APIs (e.g., URLSession, Core Data, SwiftUI).
• Only available on iOS 13+, macOS 10.15+, and other latest Apple platforms.

🔹 RxSwift vs Combine: Feature Comparison

• Platform Support
  RxSwift supports iOS 9 and above, making it suitable for apps that still need to run on older devices. Combine, on the other hand, only works on iOS 13+ and later Apple platforms.
• Ecosystem
  RxSwift has a mature ecosystem with a wide range of operators and community-driven extensions. Combine’s ecosystem is still evolving since it’s relatively new.
• Learning Curve
  RxSwift can feel steeper because it comes from the broader ReactiveX world and introduces more advanced concepts. Combine feels easier for Swift developers since it uses Swift-first patterns and Apple-style APIs.
• Integration
  RxSwift depends on third-party libraries for integration. Combine is natively integrated with Apple frameworks like URLSession, SwiftUI, and Core Data, which makes it more seamless for modern development.
• Community Support
  RxSwift has a large and well-established community, with tons of GitHub repos, tutorials, and forum discussions. Combine has official Apple documentation and growing community adoption, but it’s not as widespread as RxSwift yet.
• Performance
  Both frameworks perform excellently, but Combine benefits from being optimized by Apple for its platforms.

🔹 Example: Fetching Data from API

Let’s look at how RxSwift and Combine handle a simple task: fetching JSON from an API.

✅ Using RxSwift

import RxSwift
import RxCocoa

struct Post: Decodable {
    let id: Int
    let title: String
}
class APIService {
    func fetchPosts() -> Observable<[Post]> {
        let url = URL(string: "https://jsonplaceholder.typicode.com/posts")!
        return URLSession.shared.rx.data(request: URLRequest(url: url))
            .map { data in
                try JSONDecoder().decode([Post].self, from: data)
            }
    }
}
// Usage
let disposeBag = DisposeBag()
let api = APIService()
api.fetchPosts()
    .subscribe(onNext: { posts in
        print("Fetched Posts: \(posts.count)")
    }, onError: { error in
        print("Error: \(error)")
    })
    .disposed(by: disposeBag)

🍏 Using Combine

import Combine
import Foundation

struct Post: Decodable {
    let id: Int
    let title: String
}
class APIService {
    func fetchPosts() -> AnyPublisher<[Post], Error> {
        let url = URL(string: "https://jsonplaceholder.typicode.com/posts")!
        return URLSession.shared.dataTaskPublisher(for: url)
            .map(\.data)
            .decode(type: [Post].self, decoder: JSONDecoder())
            .eraseToAnyPublisher()
    }
}
// Usage
let api = APIService()
var cancellables = Set<AnyCancellable>()
api.fetchPosts()
    .sink(receiveCompletion: { completion in
        switch completion {
        case .failure(let error):
            print("Error: \(error)")
        case .finished:
            print("Completed")
        }
    }, receiveValue: { posts in
        print("Fetched Posts: \(posts.count)")
    })
    .store(in: &cancellables)

🔹 When to Choose RxSwift?

• You need backward compatibility (iOS 9 — iOS 12).
• Your team already has experience with ReactiveX (Android, .NET, etc.).
• You want access to a rich set of operators and mature ecosystem.

🔹 When to Choose Combine?

• You are building an iOS 13+ only app.
• You want tight integration with SwiftUI and Apple APIs.
• You prefer using an official, future-proof Apple framework.

🔹 Final Thoughts

Both RxSwift and Combine are excellent frameworks for handling asynchronous tasks in iOS.

• If you are working on modern apps (iOS 13+), Combine is the natural choice because it’s built by Apple, integrates seamlessly with SwiftUI, and is here to stay.
• If you need backward compatibility or advanced operators, RxSwift still shines as a powerful and battle-tested option.

👉 My suggestion: Start with Combine if your deployment target allows it, but keep RxSwift in your toolbox for legacy or cross-platform projects.

💡 What do you prefer — RxSwift or Combine? Share your thoughts in the comments!