swift - 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，我可以获得每个属性。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

    }
  }
}

我的问题模型我想在下面创建哪些对象

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

这就是我解决问题的方式。

第一步

由于 Question 中的 init 确实收到了 non optional 对象，我觉得 Questions 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)。

第二步

这是重构的 Question 类。如您所见，我添加了一个类方法 build，它接收一个 JSON(一个 SwiftyJSON)并返回一个 Question (如果 json 包含正确的数据)，否则为 nil。

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
        }
    }
}

第三步

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($0) }) {
            // now you have an array of optional questions [Question?]...
        }

    }
}

在 #a 行，我将所有从连接接收到的数据放入 rootJSON 中(转换为 JSON)。

第 #b 行发生了什么？

好吧，我尝试访问位于 "pack1" 中的数组。

rootJSON["pack1"].array?

如果数组存在，我运行 map 方法。这将提取数组的每个单元格，我将能够在闭包内使用 $0 参数名称引用它。

在闭包中，我使用这个 json block (应该表示一个问题)来构建一个 Question 实例。

结果将是一组 Question?。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

我无法使用真实数据尝试代码，希望这对您有所帮助。