等待任务在会话上返回。数据任务

我有一个项目,在这个项目中,我从API发送和获取数据。发送和获取它工作正常。

我的目标是等待服务器的响应(即:是|否),并根据它的情况,继续或不继续该序列,如果否,则显示警报。

对于这一部分,我有:

1. 具有客户端列表和用于添加新客户端的按钮的tableview视图。
2. 添加/编辑客户端的详细视图
3. 在详细视图上有一个保存按钮,该按钮与tableview视图相连

功能 saveClient() 获取数据并向服务器发出请求

func saveClient() -> Bool {

    let name = txtName.text ?? ""
    let address = txtAddress.text ?? ""
    let city = txtCity.text ?? ""
    let province = txtProvince.text ?? ""
    let postal_code = txtPostalCode.text ?? ""

    meal = Client(name:name, client_id: "", postal_code: postal_code, province: province, city: city, address: address)

    var jsonData = Data()
    let jsonEncoder = JSONEncoder()
    do {
        jsonData = try jsonEncoder.encode(meal)
    }
    catch {
    }
    print("a1")
    var success: Bool
    success = false

    makeRequestPost(endpoint: "http://blog.local:4711/api/clients/add",
                    requestType: "POST",
                    requestBody: jsonData,
                    completionHandler: { (response : ApiContainer<Client>?, error : Error?) in
                        if let error = error {
                            print("error calling POST on /todos")
                            print(error)
                            return
                        }
                        let b = (response?.meta)!
                        print(b.sucess)
                        if(b.sucess == "yes") {
                            success = true
                        }
                        else
                        {
                            DispatchQueue.main.async(execute: {
                                let myAlert = UIAlertController(title: "Error", message: "Error creating Client", preferredStyle: .alert)
                                let okAction = UIAlertAction(title: "Ok", style: .default, handler: nil)
                                myAlert.addAction(okAction)
                                self.present(myAlert, animated: true, completion: nil)
                            })
                            return
                        }
    } )
    return success
}

在同一控制器上:

override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {

    guard let button = sender as? UIBarButtonItem, button === btnSave else {
        return false
    }

    if !saveClient() {
        print("no sir")
        return false
    }

    print("yes sir")
    return true
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    super.prepare(for: segue, sender: sender)        
    guard let button = sender as? UIBarButtonItem, button === btnSave else {
        return
    }
}

请求功能:

func makeRequestPost<T>(endpoint: String,
                     requestType: String = "GET",
                     requestBody: Data,  completionHandler: @escaping (ApiContainer<T>?, Error?) -> ()) {

    guard let url = URL(string: endpoint) else {
        print("Error: cannot create URL")
        let error = BackendError.urlError(reason: "Could not create URL")
        completionHandler(nil, error)
        return
    }

    var urlRequest = URLRequest(url: url)
    let session = URLSession.shared

    urlRequest.httpMethod = "POST"
    urlRequest.httpBody = requestBody

    urlRequest.addValue("application/json", forHTTPHeaderField: "Content-Type")
    urlRequest.addValue("application/json", forHTTPHeaderField: "Accept")



    let task = session.dataTask(with: urlRequest, completionHandler: {
        (data, response, error) in
        guard let responseData = data else {
            print("Error: did not receive data")
            completionHandler(nil, error)
            return
        }
        guard error == nil else {
            completionHandler(nil, error!)
            return
        }

        do {
            let response = try JSONDecoder().decode(ApiContainer<T>.self, from: responseData)
            completionHandler(response, nil)
        }
        catch {
            print("error trying to convert data to JSON")
            print(error)
            completionHandler(nil, error)
        }

    })
    task.resume()
}

在控制台上,我得到:

a1级

没有,先生

对

正确的答案是:

a1级

对

是的,先生

最终注释:

1. 我尝试了一些信号量的例子。。。但它没有起作用。

2. 我在其他地方使用了一个名为“Dine”的var,并没有将其更改为客户端。但是,它不会干扰代码的这一部分