Combine vs async/await: Which One Should You Use in 2025?

In recent years, Apple introduced async/await to simplify asynchronous code in Swift. However, Combine, Apple's reactive programming framework, is still widely used. So which one should you choose in 2025?

Let’s break down both, explore real use cases, and help you make the right choice with practical Swift examples.

What is Combine?

Combine is a reactive framework introduced in iOS 13. It uses publishers, subscribers, and operators to manage asynchronous and event-driven code.

Basic Combine Example

import Combine

let publisher = Just("Hello Combine")
let subscriber = publisher
    .sink { value in
        print(value)
    }

Network Request with Combine

import Combine

struct Post: Decodable {
    let id: Int
    let title: String
}

var cancellables = Set<AnyCancellable>()

func fetchPosts() {
    URLSession.shared.dataTaskPublisher(for: URL(string: "https://jsonplaceholder.typicode.com/posts")!)
        .map(\.data)
        .decode(type: [Post].self, decoder: JSONDecoder())
        .sink(receiveCompletion: { completion in
            print(completion)
        }, receiveValue: { posts in
            print(posts)
        })
        .store(in: &cancellables)
}

What is async/await?

Introduced in Swift 5.5 (iOS 15+), async/await offers a cleaner, linear syntax for asynchronous operations. It’s part of Swift’s structured concurrency model.

Network Request with async/await

struct Post: Decodable {
    let id: Int
    let title: String
}

func fetchPosts() async {
    do {
        let (data, _) = try await URLSession.shared.data(from: URL(string: "https://jsonplaceholder.typicode.com/posts")!)
        let posts = try JSONDecoder().decode([Post].self, from: data)
        print(posts)
    } catch {
        print("Error: \(error)")
    }
}

Combine vs async/await: Key Differences

Feature	Combine	async/await
Syntax	Reactive, declarative	Sequential, readable
Error Handling	.catch, tryMap	do-catch, try
Backpressure Handling	Built-in (Operators like .debounce)	Manual (more boilerplate)
Multicasting	Built-in (.share(), .multicast)	Requires Task Groups or Shared Actors
Data Streams	Best for multiple emissions	Best for single result
Learning Curve	Steep	Easier for beginners

When to Use Each in 2025

Use Case	Recommended
Single-value async tasks (e.g. API call)	✅ async/await
Complex data streams (e.g. UI binding)	✅ Combine
SwiftUI Bindings	✅ Combine
Simpler code & readability	✅ async/await

Combine + async/await Together?

You can use both in the same app! For example, wrap Combine pipelines in async functions using .values.

func fetchData() async throws -> [Post] {
    let url = URL(string: "https://jsonplaceholder.typicode.com/posts")!

    return try await URLSession.shared
        .dataTaskPublisher(for: url)
        .map(\.data)
        .decode(type: [Post].self, decoder: JSONDecoder())
        .receive(on: DispatchQueue.main)
        .values
        .first!
}

Conclusion

• Use async/await for straightforward, sequential tasks (API calls, file I/O).
• Use Combine for more complex, multi-stream event management (form validation, real-time updates).
• In 2025, Swift’s concurrency model continues evolving — start with async/await, but don’t ignore Combine where it shines.