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，这样我就没有重复的代码？

我创建了一个方法，该方法使用 URLSession 发出网络请求，并以状态码作为参数调用完成处理程序。在完成处理中，我创建了一个条件来显示错误消息或根据状态代码执行 segue。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completionhandler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."
                        }
                    }
            })

我想重复使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 ViewController 具体的，您可以开始创建一个函数，该函数 returns 消息基于这样的状态代码：

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动到 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视图控制器的更详细错误。

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

在 Swift 中向用户显示网络错误消息

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swift

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completionhandler

urlsession