Swift wait for closure thread to finish

Question

I'm using a very simple swift project created with SPM where it includes Alamofire.

main.swift:

import Alamofire

Alamofire.request("https://google.com").responseString(queue: queue) { response in
            print("\(response.result.isSuccess)")
}

The closure is never executed if I don't use a lock. Is there a way to instruct to wait for all threads or that specific thread before exiting?

I'm aware this can be easily achieved using Playgrounds.

Answer 1

Simplest way to wait for an async task is to use a semaphore:

let semaphore = DispatchSemaphore(value: 0)

doSomethingAsync {
    semaphore.signal()
}

semaphore.wait()

// your code will not get here until the async task completes

Alternatively, if you're waiting for multiple tasks, you can use a dispatch group:

let group = DispatchGroup()

group.enter()
doAsyncTask1 {
    group.leave()
}

group.enter()
doAsyncTask2 {
    group.leave()
}

group.wait()

// You won't get here until all your tasks are done

Answer 2

For Swift 3

let group = DispatchGroup()
group.enter()
DispatchQueue.global(qos: .userInitiated).async {
    // Do work asyncly and call group.leave() after you are done
    group.leave()
}
group.notify(queue: .main, execute: {
    // This will be called when block ends             
})

This code will be helpful when you need to execute some code after some task is done.

Please add details about your question, then I can help you more.