Question

我正在尝试在我的代码中使调度组工作

let dispatchQueue:DispatchQueue = DispatchQueue(label: "com.dispatchgroup", attributes: .concurrent, target: .main)
var dispatchGroup:DispatchGroup = DispatchGroup()
func renewLoginIfRequired()->String{
    self.dispatchGroup.enter()
    dispatchQueue.async(group:dispatchGroup){
        self.authorizeApplication(completionHandler: {
            self.dispatchGroup.leave()
        })
    }
     }
    self.dispatchGroup.wait() // Stops execution here
    return "Login Success"
}

上面的代码停止在self.dispatchGroup.wait（）执行。我没有使用dispatchQueue.async（group：dispatchGroup）在self.authorizeApplication周围尝试相同的代码，但没有运气我不知道我做错了什么。这里要提到的一件事是self.authorizeApplication将在该函数中发出异步Web服务请求

编辑1：

更详细地阐述问题。我将从此方法返回一个会话令牌（String）。这是调用此

的函数

    func processPOSTRequest(_ urlString : String, isAnAuthReq:Bool = false, requestObject: Data?, onSuccess: @escaping (NSDictionary?, NSError?) -> Void, onFailure: @escaping (Data?, NSError?) -> Void){
    let manager = AFHTTPSessionManager()
    let url = URL(string: urlString);
    var request = URLRequest(url: url!);
    if !isAnAuthReq{
        let token = self.renewLoginIfRequired() //-- Get new token before processing a webservice request
        request.setValue(token, forHTTPHeaderField: "Authorization")
    }
    print("processing URl : "+urlString)
    request.httpMethod="POST";
    request.httpBody = requestObject
    request.setValue("application/json; charset=utf-8", forHTTPHeaderField:"Content-Type")
    request.setValue("application/json; charset=utf-8", forHTTPHeaderField:"Accept")
    let task = manager.dataTask(with: request, uploadProgress: nil, downloadProgress: nil, completionHandler:{ data, response, error in
        if(error == nil){
            if let responseCode = (data as? HTTPURLResponse)?.statusCode{
                if responseCode != 200 || !((response as? [String: Any])?["success"] as? Bool)!{
                    let errorResponse = NSError()
                    print("Response received for URL: "+urlString)
                    onFailure(nil, errorResponse.addItemsToUserInfo(newUserInfo: ["errorCode":String(responseCode)]))
                }
                else{
                    onSuccess(response as! NSDictionary?, nil)
                }
            }

        }
        else{
            onFailure(nil, error as NSError?)

        }
    })
    task.resume()
}

如果我使用Notify或关闭。我怎样才能做到这一点？我试过了两个

Answer 1

我不知道authorizeApplication请求的内幕是什么，但它的回调可能在主线程中执行，即在主队列中执行。因此，您可以在同一个队列中输入，离开和等待，因此在您调用self.dispatchGroup.leave()后，您无法访问self.dispatchGroup.wait()。

要处理您需要重新设计异步请求并在后台队列中调用self.dispatchGroup.leave()。

DispatchGroup无法在Swift 3中运行

1 个答案: