If you can’t manage your tasks, you will fall off your bike.

The Magic of Concurrent Queues in Swift

Published in

Paycell Tech Team

3 min readJul 31, 2024

If you’ve ever tried juggling while riding a unicycle, you probably understand the complexity of managing multiple tasks simultaneously. Fortunately, in the world of programming, we have something to help us with that: concurrent queues. Unlike juggling, using concurrent queues won’t make you fall off your unicycle or drop your precious tasks!

What Are Concurrent Queues?

Concurrent queues allow multiple tasks to run at the same time, leveraging the power of multi-core processors to improve performance and responsiveness. They are part of Grand Central Dispatch (GCD), which is Apple’s solution for managing concurrent operations in iOS and macOS applications.

Benefits of Using Concurrent Queues

✅ Improved Performance: Tasks run in parallel, reducing overall execution time.

✅ Responsiveness: Keep your app responsive by running heavy tasks in the background.

✅ Resource Utilization: Efficient use of multi-core processors.

✅ Simplified Code: GCD abstracts complex threading mechanisms, making it easier to write concurrent code.

Use Cases for Concurrent Queues

✅ Image Processing: Process multiple images simultaneously.

✅ Network Calls: Handle multiple network requests without blocking the main thread.

✅ Data Processing: Perform large data operations in the background.

✅ UI Updates: Keep the UI smooth by offloading heavy tasks.

Creating a Concurrent Queue

Creating a concurrent queue in Swift is straightforward. Here’s how you can do it:

let concurrentQueue = DispatchQueue(label: "com.example.myConcurrentQueue", attributes: .concurrent)

Executing Tasks Concurrently

To execute tasks concurrently, simply dispatch them to the queue:

concurrentQueue.async {
    print("Task 1 started")
    // Perform task 1
    print("Task 1 finished")
}

concurrentQueue.async {
    print("Task 2 started")
    // Perform task 2
    print("Task 2 finished")
}

concurrentQueue.async {
    print("Task 3 started")
    // Perform task 3
    print("Task 3 finished")
}

Using Dispatch Groups

Dispatch groups allow you to monitor a group of tasks and perform an action when all tasks are complete:

let dispatchGroup = DispatchGroup()

dispatchGroup.enter()
concurrentQueue.async {
    // Perform task
    dispatchGroup.leave()
}

dispatchGroup.enter()
concurrentQueue.async {
    // Perform another task
    dispatchGroup.leave()
}

dispatchGroup.notify(queue: DispatchQueue.main) {
    print("All tasks are complete")
}

Conclusion

Concurrent queues are a powerful tool in a developer’s arsenal, making it possible to handle multiple tasks efficiently and effectively. By using them, you can significantly improve your app’s performance and responsiveness, all while keeping your code clean and manageable. So next time you find yourself juggling multiple tasks in your app, remember: you don’t need to balance on a unicycle to keep everything in sync!

Useful Resources

The Magic of Concurrent Queues in Swift

Written by abdullahkirmizi