从Swift中的JSON对象解析多个数组

Question

我正在使用iOS app构建Swift3，并且对于应用程序的一部分，我向网页发送HTTP POST请求，该网页返回包含5个不同数组的JSON对象。我希望收到这个JSON object in Swift，并以可读格式（NSArray）使这些数组。以下是我的网页返回的内容。

{"className":["U.S. History 2 (AP)","Chemistry (HN)","Algebra 2 (HN)","Spanish 3 (HN)"],"teacherLastName":["Schartner","Racz","Johnson","Burdette"],"teacherFirstName":["Lindsey","Gregory","Shane","Joy"],"teacherTitle":["Mrs.","Mr.","Mr.","Sra."],"classID":["0001","0002","0003","0004"]}

我试图在我的Swift代码中执行以下操作。我不完全确定从哪里开始，但这是我到目前为止所做的。

func getClassList() -> NSArray{
    let myUrl = URL(string: "http://papili.us/studycentral/api/getClassList.php");
    var request = URLRequest(url:myUrl!)
    request.httpMethod = "POST"// Compose a query string
    let postString = "";
    request.httpBody = postString.data(using: String.Encoding.utf8);
    let task = URLSession.shared.dataTask(with: request) { (data: Data?, response: URLResponse?, error: Error?) in
        if error != nil {
            print("error=\(error)")
            return
        }

        // Print out response object
        print("response = \(response)")

        //Convert response sent from a server side script to a NSDictionary object:
        do {
            let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary
            if let parseJSON = json {
                // Access value of username, name, and email by its key
                let newdata : NSDictionary = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as! NSDictionary
                let info : NSArray =  newdata.value(forKey: "className") as! NSArray
                self.classList = info


            }
        } catch {
            print(error)
        }
    }
    task.resume()
    return self.classList
}

有人可以解释我需要做什么才能正确读取JSON对象中的数组吗？非常感谢你

Answer 1

凯尔，

这里有很多事情要做。您所犯的最大错误是将异步函数视为同步函数。传递给dataTask的闭包是异步执行的，这意味着在你return self.classList时它不会完成（最有可能）。为了解决这个问题，你的getClassList方法本身应该采用一个闭包，它将在数据任务完成时调用。

它看起来像这样：

func getClassList(completion: ((NSArray?, NSError?) -> Void)?) {
    let myUrl = URL(string: "http://papili.us/studycentral/api/getClassList.php");
    var request = URLRequest(url:myUrl!)
    request.httpMethod = "POST"// Compose a query string
    let postString = "";
    request.httpBody = postString.data(using: String.Encoding.utf8);
    let task = URLSession.shared.dataTask(with: request) { (data: Data?, response: URLResponse?, error: Error?) in
        if error != nil {
            print("error=\(error)")
            completion?(nil, error)
            return
        }

        // Print out response object
        print("response = \(response)")

        //Convert response sent from a server side script to a NSDictionary object:
        do {
            let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary
            if let parseJSON = json {
                // Access value of username, name, and email by its key
                let newdata : NSDictionary = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as! NSDictionary
                let info : NSArray =  newdata.value(forKey: "className") as! NSArray
                completion?(info, nil)
            }
        } catch {
            print(error)
            completion?(nil, error)
        }
    }
    task.resume()
}

你访问这些数据的方法是调用带有getClassList和NSArray?的闭包的NSError?并用它们做你想要的。这类似于你所谓的dataTask。

此外，这个请求看起来更像是GET而不是POST给我。根据您使用的API仔细检查您是否正在构建请求。

还有其他一些方法我建议清理这些代码，但我认为这些是推动你前进的要点。

Answer 2

查看此库：JSONParserSwift

您可以轻松解析JSON。

只需创建以下模型：

class BaseModel: ParsableModel {
  var className: [String]?
  var teacherLastName: [String]?
  var teacherFirstName: [String]?
  var teacherTitle: [String]?
  var classID: [String]?
}

现在调用以下方法：

do {
  let parsedModel: BaseModel = try JSONParserSwift.parse(string: jsonString)
} catch {
  print(error)
}