如何根据上一级数据获取数据

Question

我有如下 JSON。

{
  "type": "regular",
  "data": [
    {
      "title": "Title 1",
      "price_regular": 1.1,
      "price_express": 2.2,
    },
    {
      "title": "Title 2",
      "price_regular": 1.1,
      "price_express": 2.2,
    }
  ]
}

为此，我有如下模型。

struct MainModel : Codable {
    var type : String?
    var data : [DataModel]?
}

struct DataModel : Codable {
    var title : String?
    var price_regular : Float?
    var price_express : Float?
    
    var price : Float {
        get {
            if (type == "regular") { ----> Please check below query for this.
                return price_regular ?? 0.0
            }
            
            return price_express ?? 0.0
        }
    }
}

我在DataModel 中所做的是将新变量创建为price。我想检查我对主类type 有哪些数据，并在此基础上获得价格的价值。有什么办法可以做到这一点？

其实我是在做模特。我知道我可以使这个运行时，但我想在模型中执行此操作，以便逻辑仅在 1 个位置。

Answer 1

我会使用自定义init(from decoder:) 来实现，允许将类型从MainModel 传递到DataModel。

struct MainModel : Codable {
    var type : String?
    var data : [DataModel]?

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        type = try container.decode(String.self, forKey: .type)
        var dataContainer = try container.nestedUnkeyedContainer(forKey: .data)
        var dataTemp: [DataModel] = []
        while !dataContainer.isAtEnd {
            let dataSubcontainer = try dataContainer.nestedContainer(keyedBy: DataModel.DataModelKeys.self)
            let title = try dataSubcontainer.decode(String.self, forKey: .title)
            let price_regular = try dataSubcontainer.decode(Float.self, forKey: .price_regular)
            let price_express = try dataSubcontainer.decode(Float.self, forKey: .price_express)
            dataTemp.append(DataModel(title: title, price_regular: price_regular, price_express: price_express, type: type))
        }
        data = dataTemp
    }
}

struct DataModel : Codable {
    var title : String?
    var price_regular : Float?
    var price_express : Float?
    var type: String?

    enum DataModelKeys: String, CodingKey {
        case title
        case price_regular
        case price_express
    }

    var price : Float {
        get {
            if (type == "regular") {
                return price_regular ?? 0.0
            }
            return price_express ?? 0.0
        }
    }
}

测试它：

let json = """
[{
"type": "regular",
"data": [
{
  "title": "Title 1",
  "price_regular": 1.1,
  "price_express": 1.2,
},
{
  "title": "Title 2",
  "price_regular": 2.1,
  "price_express": 2.2,
}
]
},
    {
"type": "irregular",
"data": [
{
  "title": "Title 3",
  "price_regular": 1.1,
  "price_express": 1.2,
},
{
  "title": "Title 4",
  "price_regular": 2.1,
  "price_express": 2.2,
}
]
}]
"""

do {
    let model = try JSONDecoder().decode([MainModel].self, from: Data(json.utf8))
    print(model)
    model.forEach { aMainModel in
        print("MainModel type: \(aMainModel.type)")
        aMainModel.data?.forEach {
            print("Title: \($0.title) - type: \($0.type) - price: \($0.price)")
        }
    }
} catch {
    print("Error: \(error)")
}

哪个输出：

$>MainModel type: Optional("regular")
$>Title: Optional("Title 1") - type: Optional("regular") - price: 1.1
$>Title: Optional("Title 2") - type: Optional("regular") - price: 2.1
$>MainModel type: Optional("irregular")
$>Title: Optional("Title 3") - type: Optional("irregular") - price: 1.2
$>Title: Optional("Title 4") - type: Optional("irregular") - price: 2.2

Answer 2

在@Larme 回答的帮助下，我更新了模型并使其工作。

struct MainModel : Codable {
    var type : String?
    var data : [DataModel]? {
        didSet { // on didSet assigned value of type to type
            for i in 0..<(self.data ?? [DataModel]()).count {
                self.data![i].type = self.type ?? ""
            }
        }
    }
    
    
}

struct DataModel : Codable {
    var title : String?
    var price_regular : Float?
    var price_express : Float?
    
    var type : String? // added new variable
    
    var price : Float? {
        get {
            if (type == "regular") {
                return price_regular ?? 0.0
            }
            return price_express ?? 0.0
        }
    }
}

这帮助我完成了我一直在寻找的事情......