Swift函数返回值完成处理之前

Question

基本上我有一个用于将简单数据发布到服务器的代码，如果post请求成功，它将返回一个布尔值success但似乎是在处理数据之前返回了布尔值，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

这种情况正在发生，因为函数直接返回success的值，dataTask 异步，因此，函数不应该等到dataTask完成解析以编辑success的值，即return success在dataTask编辑success的值之前执行。

我建议让该函数处理 completion 闭包，而不是直接返回Bool。

您的功能应类似于：

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Swift 3中，您应该使用@escaping，有关详细信息，您可能需要查看this answer。

通话：

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

现在，它应该等到dataTask完成它的解析，然后，completion中的代码将被调用。

希望它有所帮助。