斯威夫特函数返回值之前完成处理

Question

基本上我有张贴简单的数据到服务器的代码，并会返回一个布尔值success如果POST请求是成功的，但它似乎是布尔值之前甚至返回数据被处理，我做错了什么？

public func postRequest(rawText: String) -> Bool { 
    var success = true 
    let destUrl = "http://api.getquesto.com:8080/upload/" 
    var request = URLRequest(url: URL(string: destUrl)!) 
    request.httpMethod = "POST" 
    let postString = rawText 
    request.setValue("text/plain", forHTTPHeaderField: "Content-Type") 
// request.setValue("compute", forHTTPHeaderField: "Questo-Query") 
// request.setValue("Fuck you", forHTTPHeaderField: "quizTitle") 

    request.httpBody = postString.data(using: .utf8) 
    print(request.httpBody!) 
    let task = URLSession.shared.dataTask(with: request) { data, response, error in 
     guard let data = data, error == nil else {             // check for fundamental networking error 
      print("error=\(error)") 
      success = false 
      print(success) 

      return 
     } 

     if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 {   // check for http errors 
      print("statusCode should be 200, but is \(httpStatus.statusCode)") 
      print("response = \(response)") 
     } 

     let responseString = String(data: data, encoding: .utf8) 
     do { 
      if let json = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions(rawValue: UInt(0))) as? [String: Any] { 
       print("json \(json)") 
      } else { 
       print("can not cast data") 
       success = false 

      } 
     } catch let error { 
      print("cant parse json \(error)") 
      success = false 
      print(success) 

     } 

     print("responseString = \(responseString)") 
     let dataString = NSString(data: data, encoding: String.Encoding.utf8.rawValue) 
     //print(dataString) 
     //print("responseString = \(responseString)") 
     constantVariables.rawQuestionData = dataString as! String 
     let processedResults = dataString?.replacingOccurrences(of: "\\n", with: " ") 
     print("processed results = " + (processedResults! as String)) 
     let newArray = processedResults!.components(separatedBy: ", \"") 
     //print(newArray) 

     for index in 0...(newArray.count - 1) { 
      if index%2 == 0 { 
       constantVariables.questions.insert(newArray[index].replacingOccurrences(of: "\"", with: "").replacingOccurrences(of: "]", with: "").replacingOccurrences(of: "[", with: ""), at: index/2) 

       //  ConstantsArray.questionArray.append(newArray[index]) 
       //  print("question array: " + ConstantsArray.answerArray[index/2]) 
      }else{ 
       constantVariables.answers.insert(newArray[index].replacingOccurrences(of: "\"", with: "").replacingOccurrences(of: "]", with: "").replacingOccurrences(of: "[", with: ""), at: (index-1)/2) 

       //  ConstantsArray.questionArray.append(newArray[index]) 
       print("answer array: " + constantVariables.answers[(index-1)/2]) 

      } 
     } 
    } 
    task.resume() 
    print(success) 
    return success 
    } 

Answer 1

发生这种情况，因为该函数直接返回的success值，dataTask工作异步，因此，该函数不应该等到dataTask完成解析编辑的success的值，即：return success执行之前dataTask编辑success的值。

我建议让函数处理一个completion而不是直接返回Bool。

你的功能应该是类似于：

public func postRequest(rawText: String, completion: @escaping (_ success: Bool) ->()) { 
    var success = true 
    let destUrl = "http://api.getquesto.com:8080/upload/" 
    var request = URLRequest(url: URL(string: destUrl)!) 
    request.httpMethod = "POST" 
    let postString = rawText 
    request.setValue("text/plain", forHTTPHeaderField: "Content-Type") 
    // request.setValue("compute", forHTTPHeaderField: "Questo-Query") 
    // request.setValue("Fuck you", forHTTPHeaderField: "quizTitle") 

    request.httpBody = postString.data(using: .utf8) 
    print(request.httpBody!) 
    let task = URLSession.shared.dataTask(with: request) { data, response, error in 
     guard let data = data, error == nil else {             // check for fundamental networking error 
      print("error=\(error)") 
      success = false 
      print(success) 

      return 
     } 

     if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 {   // check for http errors 
      print("statusCode should be 200, but is \(httpStatus.statusCode)") 
      print("response = \(response)") 
     } 

     let responseString = String(data: data, encoding: .utf8) 
     do { 
      if let json = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions(rawValue: UInt(0))) as? [String: Any] { 
       print("json \(json)") 
      } else { 
       print("can not cast data") 
       success = false 

      } 
     } catch let error { 
      print("cant parse json \(error)") 
      success = false 
      print(success) 

     } 

     print("responseString = \(responseString)") 
     let dataString = NSString(data: data, encoding: String.Encoding.utf8.rawValue) 
     //print(dataString) 
     //print("responseString = \(responseString)") 
     constantVariables.rawQuestionData = dataString as! String 
     let processedResults = dataString?.replacingOccurrences(of: "\\n", with: " ") 
     print("processed results = " + (processedResults! as String)) 
     let newArray = processedResults!.components(separatedBy: ", \"") 
     //print(newArray) 

     for index in 0...(newArray.count - 1) { 
      if index%2 == 0 { 
       constantVariables.questions.insert(newArray[index].replacingOccurrences(of: "\"", with: "").replacingOccurrences(of: "]", with: "").replacingOccurrences(of: "[", with: ""), at: index/2) 

       //  ConstantsArray.questionArray.append(newArray[index]) 
       //  print("question array: " + ConstantsArray.answerArray[index/2]) 
      }else{ 
       constantVariables.answers.insert(newArray[index].replacingOccurrences(of: "\"", with: "").replacingOccurrences(of: "]", with: "").replacingOccurrences(of: "[", with: ""), at: (index-1)/2) 

       //  ConstantsArray.questionArray.append(newArray[index]) 
       print("answer array: " + constantVariables.answers[(index-1)/2]) 

      } 
     } 

     completion(success) 
    } 
    task.resume() 
    print(success) 
} 

在斯威夫特3，你应该使用@escaping，以获取更多信息，您可能要检查this answer。

呼叫：

postRequest(rawText: "rawText", completion: { success in 
    print(success) 
}) 

现在，它应该等待，直到dataTask结束它的解析，然后，在completion的代码将被调用。

希望它帮助。