与完成块的Swift异步

Question

我有两个执行异步的函数。

我尝试将它们“同步”：DispatchGroup和DispatchQueue

let queue = DispatchQueue(label: "com.company.app.queue", attributes: .concurrent)
let group = DispatchGroup()

queue.async(group: group) {
    //func1
}

queue.async(group: group) {
    //func2
}

group.notify(queue: queue) {
    print("#3 finished")
}

Func1和Func2仅调用：

class func getDataFromUrl( url: URL, completion: @escaping ( Data?, URLResponse?, Error? ) -> ( ) )
    {
        URLSession.shared.dataTask( with: url )
        {
            data, response, error in

            completion( data, response, error )
        }.resume( )
    }

但问题是我不知道如何等待queue.async中的完成块..

任何人都有任何想法吗？

Answer 1

您只需使用DispatchGroup：

即可

let group = DispatchGroup()

group.enter()
API.getDataFromUrl(...) {
   // #1 Call finished
   group.leave()
}

group.enter()
API.getDataFromUrl(...) {
   // #2 Call finished
   group.leave()
}

group.notify(queue: .main)  {
    print("Both call finished")
}