How can we wait for HTTP requests to finish?

Question

Using several answers on SO, we have managed to write and execute a basic HTTP request:

import Foundation

let url:URL = URL(string: \"http://jsonplaceholder         


        

Answer 1

Using CwUtils by Matt Gallagher, I implemented a simple CountdownLatch which does the job:

import Foundation
import CwlUtils

<...>

let task = session.dataTask(with: request as URLRequest) {
    (data, response, error) in

    <...>
    latch.countDown()
}

task.resume()
latch.await()

Answer 2

The most straight-forward (and built-in) way is probably to use a DispatchSemaphore:

<...>

let sem = DispatchSemaphore(value: 0)

let task = session.dataTask(with: request as URLRequest) {
    (data, response, error) in

    <...>
    sem.signal()
}

task.resume()
sem.wait()

Answer 3

Active waiting seems to be the only way on the GCD. Using standard library material, this is what works:

import Foundation

<...>

var done = false

let task = session.dataTask(with: request as URLRequest) {
    (data, response, error) in

    <...>
    done = true
}

task.resume()

repeat {
    RunLoop.current.run(until: Date(timeIntervalSinceNow: 0.1))
} while !done