在 Swift 中向用户显示网络错误消息

Question

问题是如何使这段代码可重用，尤其是网络方法中的错误检查和完成处理程序中的条件，所以我没有重复的代码？

我创建了一个方法，该方法使用 URLSession 发出网络请求，并使用状态码作为参数调用完成处理程序。在完成处理中，我创建了一个显示错误消息或基于状态码执行 segue 的条件。所有这些代码都有效，但我想让它可重用，所以我没有重复的代码。

联网方式：

func saveMessage(data: String, day: String, completion: @escaping (Int)->()) {
    let url = URL(string: "\(Constants.baseURL)/daily_mindset/today_message")
    guard let requestUrl = url else { fatalError() }
    var request = URLRequest(url: requestUrl)
    request.httpMethod = "POST"
    
    // Set HTTP Request Header
    request.setValue("application/json", forHTTPHeaderField: "Accept")
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")
    
    let jsonData = encodeJSON(with: data, day: day)
    request.httpBody = jsonData
    
    let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
        if error != nil {
            completion(700)
            return
        }
        
        guard let response = response as? HTTPURLResponse else {
            completion(701)
            return
        }

        guard (200...299).contains(response.statusCode) else {
            completion(response.statusCode)
            return
        }
        
        guard let mime = response.mimeType, mime == "application/json" else {
            completion(702)
            return
        }
        
        guard let data = data else {
            completion(703)
            return
        }
        
        do {
            let todoItemModel = try JSONDecoder().decode(MessageData.self, from: data)
            Constants.currentMindsetId = todoItemModel._id!
            print("Response data:\n \(todoItemModel)")
        } catch let jsonErr{
            print(jsonErr)
        }
        completion(response.statusCode)
    }
    task.resume()
}

使用完成处理程序调用网络方法：

messageManager.saveMessage(data: textView.text, day: day, completion: {(statusCode: Int) -> Void in
                    if (200...299).contains(statusCode) {
                        DispatchQueue.main.async {
                            self.performSegue(withIdentifier: "ToDailyMindsetScreen", sender: sender)
                        }
                    } else if (400...499).contains(statusCode) {
                        DispatchQueue.main.async {
                            self.errorLabel.text = "Please make sure you filled in the all the required fields."
                        }
                    } else if (500...599).contains(statusCode) {
                        DispatchQueue.main.async {
                            self.errorLabel.text = "Sorry, couldn't reach our server."
                        }
                    } else if (700...).contains(statusCode) {
                        DispatchQueue.main.async {
                            self.errorLabel.text = "Sorry, something went wrong. Try again later."
                        }
                    }
            })

我想重用的网络方法中的代码：

if error != nil {
            completion(700)
            return
        }
        
        guard let response = response as? HTTPURLResponse else {
            completion(701)
            return
        }

        guard (200...299).contains(response.statusCode) else {
            completion(response.statusCode)
            return
        }
        
        guard let mime = response.mimeType, mime == "application/json" else {
            completion(702)
            return
        }
        
        guard let data = data else {
            completion(703)
            return
        }

我想重用的完成处理程序中的代码：

if (200...299).contains(statusCode) {
                        DispatchQueue.main.async {
                            self.performSegue(withIdentifier: "ToDailyMindsetScreen", sender: sender)
                        }
                    } else if (400...499).contains(statusCode) {
                        DispatchQueue.main.async {
                            self.errorLabel.text = "Please make sure you filled in the all the required fields."
                        }
                    } else if (500...599).contains(statusCode) {
                        DispatchQueue.main.async {
                            self.errorLabel.text = "Sorry, couldn't reach our server."
                        }
                    } else if (700...).contains(statusCode) {
                        DispatchQueue.main.async {
                            self.errorLabel.text = "Sorry, something went wrong. Try again later."
                        }
                    }

Answer 1

如果错误消息是特定于 ViewController 的，您可以从创建一个函数开始，该函数根据状态代码返回消息，如下所示：

private func getErrorMessageFor(statusCode: Int) -> String? {
    if (200...299).contains(statusCode) {
        //If no error message is returned assume that the request was a success
        return nil
    } else if (400...499).contains(statusCode) {
        return "Please make sure you filled in the all the required fields."
    } else if (500...599).contains(statusCode) {
        return "Sorry, couldn't reach our server."
    } else if (700...).contains(statusCode) {
        return "Sorry, something went wrong. Try again later."
    } else {
        return "Message for other errors?"
    }
}

您始终可以将此代码移至 ViewController 子类以提供更通用的错误消息，并在以后覆盖它以提供特定 View Controller 的更详细的错误。

class BaseViewController: UIViewController {
    func getErrorMessageFor(statusCode: Int) -> String? {
        //base implementation here
    }
}

class OtherViewController: BaseViewController {
    override func getErrorMessageFor(statusCode: Int) -> String? {
        //create a new error message only for statusCode 404
        if statusCode == 404 {
            return "The requested resource was not found on the server. Please contact the support team"
        } else {
            return super.getErrorMessageFor(statusCode: statusCode)
        }
    } 
}

请记住，随着应用程序的增长，您可能希望创建一个 APIClient 来为您处理网络和错误处理。看看https://bustoutsolutions.github.io/siesta/，很人性化