如何从 SwiftyJSON 创建对象

Question

我有一个代码，可以解析 JSON 的问题列表，我可以得到每个属性。如何遍历整个文件并为每个问题创建一个对象？

class ViewController: UIViewController {

var hoge: JSON?

override func viewDidLoad() {
    super.viewDidLoad()

    let number = arc4random_uniform(1000)
    let url = NSURL(string: "http://www.wirehead.ru/try-en.json?\(number)")
    var request = NSURLRequest(URL: url!)
    var data = NSURLConnection.sendSynchronousRequest(request, returningResponse: nil, error: nil)
    if data != nil {
        hoge = JSON(data: data!)
        let level = hoge!["pack1"][0]["level"].intValue
        let questionText = hoge!["pack1"][0]["questionText"].stringValue
        let answer1 = hoge!["pack1"][0]["answer1"].stringValue
        let answer2 = hoge!["pack1"][0]["answer2"].stringValue
        let answer3 = hoge!["pack1"][0]["answer3"].stringValue
        let answer4 = hoge!["pack1"][0]["answer4"].stringValue
        let correctAnswer = hoge!["pack1"][0]["correctAnswer"].stringValue
        let haveAnswered = hoge!["pack1"][0]["haveAnswered"].boolValue

    }
  }
}

我想在下面创建哪些对象的问题模型

class Question {

    var level : Int?
    var questionText : String?
    var answer1 : String?
    var answer2 : String?
    var answer3 : String?
    var answer4 : String?
    var correctAnswer : String?
    var haveAnswered : Bool = false

    init(level: Int, questionText:String, answer1:String, answer2:String, answer3:String, answer4:String, correctAnswer: String, haveAnswered:Bool) {
        self.level = level
        self.questionText = questionText
        self.answer1 = answer1
        self.answer2 = answer2
        self.answer3 = answer3
        self.answer4 = answer4
        self.correctAnswer = correctAnswer
        self.haveAnswered = false
    }

}

Answer 1

这就是我处理问题的方式。

第 1 步

由于 Question 中的 init 确实收到了 non optional 对象，我觉得问题的属性也应该是非可选的。我还将属性从 var 转换为 let（如果我错了请告诉我）。

第 2 步

这是重构后的 Question class。如您所见，我添加了一个 class 方法 build，它接收一个 JSON（一个 SwiftyJSON）和一个 returns 一个 Question（如果 json 包含正确的数据），否则为零。

Right now I cannot do this with a failable initializer.

extension String {
    func toBool() -> Bool? {
        switch self.lowercaseString {
        case "true", "1", "yes" : return true
        case "false", "0", "no" : return false
        default: return nil
        }
    }
}

class Question {

    let level: Int
    let questionText: String
    let answer1: String
    let answer2: String
    let answer3: String
    let answer4: String
    let correctAnswer: String
    let haveAnswered: Bool

    init(level: Int, questionText:String, answer1:String, answer2:String, answer3:String, answer4:String, correctAnswer: String, haveAnswered:Bool) {
        self.level = level
        self.questionText = questionText
        self.answer1 = answer1
        self.answer2 = answer2
        self.answer3 = answer3
        self.answer4 = answer4
        self.correctAnswer = correctAnswer
        self.haveAnswered = false
    }

    class func build(json:JSON) -> Question? {
        if let
            level = json["level"].string?.toInt(),
            questionText = json["questionText"].string,
            answer1 = json["answer1"].string,
            answer2 = json["answer2"].string,
            answer3 = json["answer3"].string,
            answer4 = json["answer4"].string,
            correctAnswer = json["correctAnswer"].string,
            haveAnswered = json["haveAnswered"].string?.toBool() {
                return Question(
                    level: level,
                    questionText: questionText,
                    answer1: answer1,
                    answer2: answer2,
                    answer3: answer3,
                    answer4: answer4,
                    correctAnswer: correctAnswer,
                    haveAnswered: haveAnswered)
        } else {
            debugPrintln("bad json \(json)")
            return nil
        }
    }
}

步骤 3

现在让我们看看viewDidLoad。

func viewDidLoad() {
    super.viewDidLoad()

    let number = arc4random_uniform(1000)

    if let
        url = NSURL(string: "http://www.wirehead.ru/try-en.json?\(number)"),
        data = NSURLConnection.sendSynchronousRequest(NSURLRequest(URL: url), returningResponse: nil, error: nil) {
        // line #a
        let rootJSON = JSON(data: data) 
        // line #b
        if let questions = (rootJSON["pack1"].array?.map { return Question.build([=11=]) }) {
            // now you have an array of optional questions [Question?]...
        }

    }
}

在第 #a 行，我在 rootJSON 中放入了从连接接收到的全部数据（转换为 JSON）。

第 #b 行发生了什么？

好吧，我尝试访问位于 "pack1" 内的数组。

rootJSON["pack1"].array?

如果数组存在我运行映射方法。这将提取数组的每个单元格，我将能够在闭包内使用 [=28=] 参数名称引用它。

在闭包中，我使用这个 json 块（应该代表一个问题）来构建一个 Question 实例。

结果将是 Question? 的数组。如果某些子数据无效，则可能存在不良值。如果你愿意，我可以告诉你如何从这个数组

中删除 nil 值

我无法用真实数据尝试代码，希望这对您有所帮助。

Answer 2

for (item, content) in hoge {
    let level = content["level"].intValue
}

应该可行

Answer 3

第 1 步。我们将创建一个协议，其中包含一个构造方法和模型 class

protocol JSONable {
    init?(parameter: JSON)
}

class Style: JSONable {
    let ID              :String!
    let name            :String!

    required init(parameter: JSON) {
        ID            = parameter["id"].stringValue
        name          = parameter["name"].stringValue
    }

    /*  JSON response format
    {
      "status": true,
      "message": "",
      "data": [
        {
          "id": 1,
          "name": "Style 1"
        },
        {
          "id": 2,
          "name": "Style 2"
        },
        {
          "id": 3,
          "name": "Style 3"
        }
      ]
    }
    */
}

第 2 步。我们将创建 JSON 的扩展，它将 JSON 转换为模型 class 类型对象

extension JSON {
    func to<T>(type: T?) -> Any? {
        if let baseObj = type as? JSONable.Type {
            if self.type == .array {
                var arrObject: [Any] = []
                for obj in self.arrayValue {
                    let object = baseObj.init(parameter: obj)
                    arrObject.append(object!)
                }
                return arrObject
            } else {
                let object = baseObj.init(parameter: self)
                return object!
            }
        }
        return nil
    }
}

第 3 步。将代码与 Alamofire 或其他代码一起使用。

Alamofire.request(.GET, url).validate().responseJSON { response in
        switch response.result {
            case .success(let value):
                let json = JSON(value)

                var styles: [Style] = []
                if let styleArr = json["data"].to(type: Style.self) {
                    styles = styleArr as! [Style]
                }
                print("styles: \(styles)")
            case .failure(let error):
                print(error)
        }
 }

希望对您有所帮助。

有关这方面的更多信息，请参阅此 link。
https://github.com/SwiftyJSON/SwiftyJSON/issues/714

Answer 4

您可以使用专门为此目的设计的 SwiftyJSONModel。因此，在您的情况下，模型将是这样的：

class Question: JSONObjectInitializable {
    enum PropertyKey: String {
        case level, questionText
        case answer1, answer2, answer3, answer4
        case correctAnswer, haveAnswered
    }

    var level : Int?
    var questionText : String?
    var answer1 : String?
    var answer2 : String?
    var answer3 : String?
    var answer4 : String?
    var correctAnswer : String?
    var haveAnswered : Bool = false

    required init(object: JSONObject<PropertyKey>) throws {
        level = object.value(for: .level)
        questionText = object.value(for: .questionText)
        answer1 = object.value(for: .answer1)
        answer2 = object.value(for: .answer2)
        answer3 = object.value(for: .answer3)
        answer4 = object.value(for: .answer4)
        correctAnswer = object.value(for: .correctAnswer)
        haveAnswered = object.value(for: .haveAnswered) ?? false
    }   
}

然后这样做：

let rootJSON = JSON(data: data)
let questions = rootJSON.arrayValue.flatMap { try? Question(json: [=11=]) }

该框架为您提供了几个不错的功能：

所有的键都存储在单独的枚举中PropertyKey
没有样板，如 stringValue、intValue 等
如果 JSON 无效，框架将给出一个详细的错误，您将立即看到到底出了什么问题

如何从 SwiftyJSON 创建对象

How to create objects from SwiftyJSON

swift

swifty-json

第 1 步

第 2 步

步骤 3