GCD.swift

gistfile1.txt

import Foundation

//let queue = DispatchQueue.global()
//let group = DispatchGroup()
//let n = 9
//for i in 0..<n {
//    queue.async(group: group) {
//        print("\(i): Running async task...")
//        sleep(3)
//        print("\(i): Async task completed")
//    }
//}
//group.wait()
//print("done")

func startLoad() -> String {
    var string = ""
    let url = URL(string: "https://postman-echo.com/get?foo1=bar1&foo2=bar2")!
//    let semaphore = DispatchSemaphore(value: 0)
    let queue = DispatchQueue.global()
    let group = DispatchGroup()

    let task = URLSession.shared.dataTask(with: url) { data, response, error in
        if let error = error {
            print(error)
            return
        }
        guard let httpResponse = response as? HTTPURLResponse,
            (200...299).contains(httpResponse.statusCode) else {
                print(response.debugDescription)
            return
        }
        if let mimeType = httpResponse.mimeType, mimeType == "application/json",
            let data = data {
            string = String(data: data, encoding: .utf8) ?? ""
//            print(string)
//            DispatchQueue.main.async {
//                self.webView.loadHTMLString(string, baseURL: url)
//            }
        }
        group.leave()
//        semaphore.signal()
    }
    queue.async(group: group) {
        group.enter()
        task.resume()
    }
//    _ = semaphore.wait(timeout: DispatchTime.now().advanced(by: DispatchTimeInterval.seconds(2)))
//    }
//    group.wait()
//    group.notify(queue: queue) {
//        return "---> " + string
//    }
//    sleep(3)
    group.wait()
    return string
}

print("Loaded value = " + startLoad())