Can synchronization (synchronized) be applied to a variable?

No, the keyword synchronized does not exist in Swift. Other mechanisms are used for synchronizing access to variables in multithreaded environments:

• Dispatch Queues: Serial queues allow executing code blocks sequentially, ensuring that only one thread works with the variable at a time.

  // Serial queue for synchronization
  let queue = DispatchQueue(label: "com.myapp.syncQueue")
  
  var sharedVariable = 0
  
  func updateSharedVariable() {
      queue.sync {
          // Synchronous access to the variable within the queue
          sharedVariable += 1
          print(sharedVariable)
      }
  }
  

• NSLock/NSRecursiveLock: Allow locking access to a code section.

  import Foundation
  
  let lock = NSLock()
  var sharedArray = [Int]()
  
  func addToSharedArray(value: Int) {
      lock.lock() // Acquire mutex
      sharedArray.append(value)
      print("Added: \(value). Array: \(sharedArray)")
      lock.unlock() // Release mutex
  }
  

• Operations and Operation Queues: Provide a high-level way to manage parallel tasks, including dependencies and priorities.

• @synchronized (Objective-C): An analogous mechanism existed in Objective-C, but it is not directly available in Swift and requires bridging with Objective-C. It is recommended to use Swift-native solutions (Dispatch Queues, Locks).

The choice of mechanism depends on the specifics of the task. Dispatch Queues are often the most convenient and efficient way for simple synchronization of data access.