Junior — Middle

Have you ever worked with Dispatch Barrier mechanism for thread synchronization?

sobes.tech AI

Answer from AI

Yes, I have worked with Dispatch Barrier in GCD (Grand Central Dispatch) for thread synchronization in iOS.

Dispatch Barrier allows executing a block of code exclusively on a queue that supports barriers, usually on a concurrent queue. This means that all tasks submitted before the barrier complete, then the barrier block executes, and only after its completion do the remaining tasks continue.

Example of usage:

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

queue.async {
    print("Task 1")
}

queue.async {
    print("Task 2")
}

queue.async(flags: .barrier) {
    print("Barrier task — exclusive access")
}

queue.async {
    print("Task 3")
}

This is useful when you need to ensure exclusive access to a shared resource for writing, while allowing parallel execution of read tasks.

Dispatch Barrier is a convenient way to synchronize without explicitly using locks.

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