IOS Swift Question posted in
The official documentation can be found here.

Ios swift – How to implement a concurrency-safe static variable in Swift 6?

I’m working on a Swift 6 project and need to manage a static variable that stores network responses. The current implementation isn’t concurrency-safe because multiple threads can access and modify the shared state, leading to race conditions. Previously this code worked on Swift 4.

extension NetworkRequestHandler {
// Basic static variable with concurrency issues
static private var cachedResponses: [NetworkResponse] = []

// Adding a response
static func addResponse(_ response: NetworkResponse) {
    cachedResponses.append(response)
}

// Removing all responses
static func clearResponses() {
    cachedResponses.removeAll()
}
}


private extension NetworkRequestHandler {
    // Helper function to retrieve the response for a specific request
    static func response(for request: URLRequest) -> NetworkResponse? {
        return cachedResponses.first { $0.url == request.url }
    }
}

So basically the problem is in this part of code static private var cachedResponses: [NetworkResponse] = [] with error – Static property ‘cachedResponses’ is not concurrency-safe because it is nonisolated global shared mutable state

Tags:

2

Answers


  1. 0

    You could use an actor instead of that static property and add the actor as a property in your network type

    actor ResponseCache {
    private var cachedResponses: [NetworkResponse] = []

    func addResponse(_ response: NetworkResponse) {
        cachedResponses.append(response)
    }

    func clearResponses() {
        cachedResponses.removeAll()
    }

    func get(_ url: URL) -> NetworkResponse? {
        cachedResponses.first { $0.url == url }
    }
}

    private extension NetworkRequestHandler {
    func response(for request: URLRequest) async -> NetworkResponse? {
        guard let url = request.url else { return nil }

        return await cachedResponses.get(url)
    }
}
    Login or Signup to reply.
  2. 0

    Just make your files as an actor like below I do:

    actor SingletonWithStatic {
  private init() { }
  private var output = ""
  static let shared = SingletonWithStatic()

  func prepare(outputLine line: String) {
    output += line
    output += "n"
  }

  func flushOutput() {
    print(output)
    output = ""
  }
}

    Or you can silent your warning by making your static variable unsafe, but make sure you use that static variable in thread safe manner.

    class SingletonWithStatic {
  private init() { }
  private var output = ""
  nonisolated(unsafe) static let shared = SingletonWithStatic()

  func prepare(outputLine line: String) {
    output += line
    output += "n"
  }

  func flushOutput() {
    print(output)
    output = ""
  }
}

    Or mark your class or struct as @MainActor

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search