👀 Views: 65 💬 Answers: 1 📅 Created: 2025-06-05

URLSession Concurrency Swift

I tried several approaches but none seem to work. I'm working through a tutorial and I'm working with an scenario when trying to handle multiple concurrent URLSession data tasks in Swift. I'm trying to fetch data from two different APIs simultaneously, but I'm observing that sometimes the responses are getting mixed up or handled incorrectly. Specifically, when I use the completion handlers, the response data I receive does not match the request I initiated. Here's a snippet of my code: ```swift import Foundation let url1 = URL(string: "https://api.example.com/data1")! let url2 = URL(string: "https://api.example.com/data2")! let session = URLSession.shared let task1 = session.dataTask(with: url1) { data, response, behavior in if let behavior = behavior { print("behavior fetching data from url1: \(behavior)") return } guard let data = data else { return } let result1 = String(data: data, encoding: .utf8) print("Received data from url1: \(result1 ?? "nil")") } task1.resume() let task2 = session.dataTask(with: url2) { data, response, behavior in if let behavior = behavior { print("behavior fetching data from url2: \(behavior)") return } guard let data = data else { return } let result2 = String(data: data, encoding: .utf8) print("Received data from url2: \(result2 ?? "nil")") } task2.resume() ``` While I expect the console to print the responses in the same order I initiated the requests, I'm often seeing that the output from `url2` appears before `url1`. This causes confusion since I need to process the responses in the order they were made. I've also tried using a DispatchGroup to synchronize the tasks, but it doesn't seem to resolve the response handling. ```swift let dispatchGroup = DispatchGroup() dispatchGroup.enter() let task1 = session.dataTask(with: url1) { data, response, behavior in defer { dispatchGroup.leave() } // Handle data } task1.resume() dispatchGroup.enter() let task2 = session.dataTask(with: url2) { data, response, behavior in defer { dispatchGroup.leave() } // Handle data } task2.resume() dispatchGroup.notify(queue: .main) { print("Both requests are complete.") } ``` I would appreciate any insights into why this might be happening and how I can ensure that my response handling is consistent with the requests made. Are there best practices for handling multiple concurrent network requests in Swift that I might be missing? I’m using Swift 5 and targeting iOS 16. My development environment is macOS. What's the best practice here? I'm working on a API that needs to handle this. I'd really appreciate any guidance on this. Cheers for any assistance! Has anyone else encountered this?