Multithreading executing multiple tasks in parallel in swift ios

问题

I know creation of queues and able to execute single task but how can i execute multiple tasks in parallel.

Concurrent Queue ---->

let concurrentQueue = DispatchQueue(label: "com.some.concurrentQueue", attributes: .concurrent)
concurrentQueue.async {
    //executable code

}

BackgroundQueue without priorities default--->

DispatchQueue.global().async {
    //executable code
}

Backgroundqueue with priorities---->

DispatchQueue.global(qos: .userInitiated).async { //.userInteractive .background .default .unspecified
    //executable code
}

Getting back to the main Queue ---->

DispatchQueue.main.async {
     //executable code
}

All are asynchronous but how can i execute multiple methods at a time how should i code in swift.

回答1:

If you have a for loop method that calls a method and you want to calls this methods concurrent, so just use this :

DispatchQueue.concurrentPerform(iterations: Int, execute: { (count) in
   doSomethingFor(count: count)
}

But if you have some individuals methods that you want to call concurrent, just do like this:

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

concurrentQueue.async {
    //executable code
    myFirstMethod()
}

concurrentQueue.async {
    //executable code
       mySecondMethod()
}

This way concurrentQueue, will manages your tasks concurrently itself.

来源：https://stackoverflow.com/questions/50042458/multithreading-executing-multiple-tasks-in-parallel-in-swift-ios