Question

我试图在for in循环中运行一个函数X次，但是当所有函数返回后，我想运行另一个函数。

当前，我通过将最后一个功能延迟1秒钟来使其工作，但我真的很想让Dispatch Group工作。

我已经遍历各种在线示例和其他问题，但是我尝试的任何方法似乎都不起作用，目前我所知道的代码将不起作用，因为每次for函数中都运行dispatchGroup.leave（）时，而不是返回时发送。

我尝试将DispatchGroup代码放入函数（位于另一个文件中），但是我很困惑，但是我认为我已经接近解决方案了。

我还查看了信号量，并在每次循环运行时使用count并增加一个值，但是我一直回到DispatchGroups。

我最后的办法就是问一个问题！

ViewController代码

 @IBAction func removeDeviceBtn(_ sender: Any) {

    let dispatchGroup = DispatchGroup()

    for owner in arrOwnerList {
        dispatchGroup.enter()
        self.removeDevice(device: self.device, account: owner as! String, completion: self.completed)
        dispatchGroup.leave()
    }

    dispatchGroup.notify(queue: DispatchQueue.main, execute: {
        self.removeDeviceFromServer(device: self.device)
        self.sendEmail(to:"gordon@example.co.uk", subject:self.device+" has been removed", text:self.device+" has been removed from the server, please check the sim for bar and termination")
    })

其他文件中的功能代码作为扩展名

  func completed(isSuccess: Bool) {
}

func removeDevice(device: String, account: String, completion: @escaping (Bool) -> Void) {

    let dictHeader : [String:String] = ["username":Username,"password":Password]
    let dictArray = [device]

    WebHelper.requestPUTAPIRemoveDevice(BaseURL+"rootaccount/removedevices/"+account+"?server=MUIR", header: dictHeader, dictArray: dictArray, controllerView: self, success: { (response) in
        if response.count == 0 {
            DispatchQueue.main.async {
                GlobalConstant.showAlertMessage(withOkButtonAndTitle: GlobalConstant.AppName, andMessage: Messages.ServerError, on: self)
            }
        }
        else {
            if response.count != 0 {
                let isSuccess = true
                completion(isSuccess)
            }
            else{
                DispatchQueue.main.async {
                    GlobalConstant.showAlertMessage(withOkButtonAndTitle: GlobalConstant.AppName, andMessage: Messages.NoDataFound, on: self)

                }
            }
        }
    }) { (error) in
        DispatchQueue.main.async {
            GlobalConstant.showAlertMessage(withOkButtonAndTitle: GlobalConstant.AppName, andMessage: error?.localizedDescription ?? Messages.ServerError, on: self)
        }
    }
}

WebHelper文件中的代码

    class func requestPUTAPIRemoveDevice(_ strURL: String,header: Dictionary<String,String>,dictArray: Array<Any>, controllerView viewController: UIViewController, success: @escaping (_ response: [AnyHashable: Any]) -> Void, failure: @escaping (_ error: Error?) -> Void) {

    if GlobalConstant.isReachable() {
        DispatchQueue.main.async {
            LoadingIndicatorView.sharedInstance.showHUD()
        }
        let loginString = String(format: "%@:%@", header["username"]!, header["password"]!)
        let loginData: Data = loginString.data(using: String.Encoding.utf8)!
        let base64LoginString = loginData.base64EncodedString(options: NSData.Base64EncodingOptions())

        let headers = ["Authorization": "Basic "+base64LoginString, "Referer": "http://www.example.com"]

        let postData = try? JSONSerialization.data(withJSONObject: dictArray, options: [])

        let request = NSMutableURLRequest(url: NSURL(string: strURL)! as URL,
                                          cachePolicy: .useProtocolCachePolicy,
                                          timeoutInterval: 10.0)
        request.httpMethod = "PUT"
        request.allHTTPHeaderFields = headers
        request.httpBody = postData

        let session = URLSession.shared
        let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
            if (error != nil) {
                DispatchQueue.main.async {
                    LoadingIndicatorView.sharedInstance.hideHUD()
                }
                failure(error)
            } else {
                if let httpResponse = response as? HTTPURLResponse {
                    print("Server code \(httpResponse.statusCode)")
                    if httpResponse.statusCode == 200 || httpResponse.statusCode == 208 {
                        DispatchQueue.main.async {
                            LoadingIndicatorView.sharedInstance.hideHUD()
                        }
                        let jsonResult = try? JSONSerialization.jsonObject(with: data!, options:    JSONSerialization.ReadingOptions.mutableContainers)

                        if (jsonResult is NSDictionary) {
                            success(jsonResult as! [AnyHashable : Any])
                        }
                        else if (jsonResult is NSArray) {
                            success(["response":jsonResult as! NSArray])
                        }
                        else{
                          success(["response":httpResponse.statusCode])
                          DispatchQueue.main.async {
                        }

                        }
                    }
                    else{
                        DispatchQueue.main.async {
                            LoadingIndicatorView.sharedInstance.hideHUD()
                        }
                        failure(error)
                    }
                }
            }
        })

        dataTask.resume()
    }
    else {
        DispatchQueue.main.async {
            LoadingIndicatorView.sharedInstance.hideHUD()
            GlobalConstant.showAlertMessage(withOkButtonAndTitle: "", andMessage: "Internet not connected", on: viewController)
        }

    }
}

最终的解决方案（除了整理各种其他问题）是将success(["response":httpResponse.statusCode])添加到WebHelper文件中，上面的代码已更正

Answer 1

将leave放在完成处理程序中：

for owner in arrOwnerList {
    dispatchGroup.enter()
    removeDevice(device: device, account: owner as! String) { [weak self] success in
        self?.completed(isSuccess: success)
        dispatchGroup.leave()
    }
}

或者鉴于您实际上并没有在completed函数中做任何事情，我将其删除：

for owner in arrOwnerList {
    dispatchGroup.enter()
    removeDevice(device: device, account: owner as! String) { _ in
        dispatchGroup.leave()
    }
}

我注意到您在removeDevice中有执行路径，它们没有调用完成处理程序。确保每个执行路径都调用完成处理程序，否则您的调度组将永远不会得到解决。

func removeDevice(device: String, account: String, completion: @escaping (Bool) -> Void) {

    let dictHeader = ["username": Username, "password": Password]
    let dictArray = [device]

    WebHelper.requestPUTAPIRemoveDevice(BaseURL+"rootaccount/removedevices/"+account+"?server=MUIR", header: dictHeader, dictArray: dictArray, controllerView: self, success: { response in
        DispatchQueue.main.async {
            if response.count == 0 {
                GlobalConstant.showAlertMessage(withOkButtonAndTitle: GlobalConstant.AppName, andMessage: Messages.ServerError, on: self)
                completion(false)
            } else {
                completion(true)
            }
        }
    }, failure: { error in
        DispatchQueue.main.async {
            GlobalConstant.showAlertMessage(withOkButtonAndTitle: GlobalConstant.AppName, andMessage: error?.localizedDescription ?? Messages.ServerError, on: self)
            completion(false)
        }
    })
}

顺便说一句，我不知道“失败”关闭的名称，因此我假设它是failure，但可以根据您的requestPUTAPIRemoveDevice方法的要求进行调整。我们通常会在Swift中避免使用多重闭包模式，但是如果您要这样做，我会避免使用尾随的闭包语法。它使第二次关闭的功能意图更加明确。

或者，所有这些都引出了一个问题，为什么requestPUTAPIRemoveDevice根本就启动了UI更新。我可能会将其放在视图控制器方法中。因此requestPUTAPIRemoveDevice应该只传回足够的信息，以便removeDeviceBtn例程知道出现什么错误。对于每个故障显示单独的错误消息的想法也可能是可疑的。（例如，如果您失去了互联网连接，并试图删除许多设备，您是否真的要显示许多单独的错误消息？）但这不在此问题的范围内。

调度组命令在代码中的何处？

1 个答案: