ios - 尝试在 iOS 中解析动态 JSON

Question

我生成了以下 JSON 示例 block 。任何以字母结尾的值都是动态的。

{
    "groupName": {
        "groupA": {
            "fields": {
                "fieldA": "valueA",
                "fieldB": "valueB"
            },
            "letters": {
                "letterA: "A"
            }
        },
        "groupB": {
            "fields": {
                "fieldC": "valueC",
                "fieldD": "valueD"
            },
            "letters": {
                "letterB: "B"
            }
        }
    }
}

我的目标是使用 Decodable，这样我就可以将这些数据读入我定义的 struct 中。

下面是我用来尝试解决此问题的 playground 文件中包含的当前工作:

import Foundation

let jsonString = "{\"groupName\":{\"groupA\":{\"fields\":{\"fieldA\":\"valueA\",\"fieldB\":\"valueB\"},\"letters\":{\"letterA:\"A\"}},\"groupB\":{\"fields\":{\"fieldC\":\"valueC\",\"fieldD\":\"valueD\"},\"letters\":{\"letterB:\"B\"}}}}"

struct CustomCodingKeys: CodingKey {
    var intValue: Int?
    var stringValue: String

    init?(intValue: Int) { self.intValue = intValue; self.stringValue = "\(intValue)" }
    init?(stringValue: String) { self.stringValue = stringValue }

    static let field = CustomCodingKeys.make(key: "field")

    static func make(key: String) -> CustomCodingKeys {
        return CustomCodingKeys(stringValue: key)!
    }
}

// Values
struct Field {
    let field: String
    let value: String
}

struct Letter: Decodable {
    let title: String
    let letter: String
}

// Value holders
struct FieldData: Decodable {
    var fields: [Field]

    init(from decoder: Decoder) throws {
        self.fields = [Field]()
        let container = try decoder.container(keyedBy: CustomCodingKeys.self)
        for key in container.allKeys {
            print("processing field: \(key.stringValue)")
            let dynamicKey = CustomCodingKeys.make(key: key.stringValue)
            let value = try container.decode(String.self, forKey: dynamicKey)
            let field = Field(field: key.stringValue,
                              value: value)
            fields.append(field)
        }
    }
}

struct LetterData: Decodable {
    var letters: [Letter]

    init(from decoder: Decoder) throws {
        self.letters = [Letter]()
        let container = try decoder.container(keyedBy: CustomCodingKeys.self)
        for key in container.allKeys {
            print("processing letter: \(key.stringValue)")
            let dynamicKey = CustomCodingKeys.make(key: key.stringValue)
            let value = try container.decode(String.self, forKey: dynamicKey)
            let letter = Letter(title: key.stringValue,
                                letter: value)
            letters.append(letter)
        }
    }
}

// Containers
struct Group: Decodable {
    var name: String!
    var groups: [GroupData]

    init(from decoder: Decoder) throws {
        self.groups = [GroupData]()
        let container = try decoder.container(keyedBy: CustomCodingKeys.self)
        for key in container.allKeys {
            print("processing section: \(key.stringValue)")
            let group = try container.decode(GroupData.self,
                                             forKey: key)
            groups.append(group)
        }
    }
}

struct GroupData: Decodable {
    var fieldData: FieldData
    var letterData: LetterData

    enum CodingKeys: String, CodingKey {
        case fieldData = "fields"
        case letterData = "letters"
    }
}

struct GroupList: Decodable {
    struct GroupName: Decodable {
        var name: String!
        var groups: [Group]

        init(from decoder: Decoder) throws {
            self.groups = [Group]()

            let container = try decoder.container(keyedBy: CustomCodingKeys.self)
            for key in container.allKeys {
                let name = key.stringValue
                self.name = name
                print("processing group: \(String(describing: self.name))")
                var group = try container.decode(Group.self,
                                                 forKey: key)
                group.name = name
                groups.append(group)
            }
        }
    }

    let groupName: GroupName
}

let decoder = JSONDecoder()
if let data = jsonString.data(using: .utf8),
    let groupList = try? decoder.decode(GroupList.self,
                                        from: data) {
    print("group list created")
}

在我的 GroupData 结构中，我可以删除变量然后实现 init(from decoder: Decoder) throws，当配置了正确的查找(FieldData & LetterData inits)，可以识别正确的对。但是，它不会填充正确的值结构。

Answer 1

你在解码 Group 时犯了一个小错误。您倾向于解码 Group 中组的所有键，并且您还进一步传递解码 GroupData 本身具有“字段”和“字母”。在 Group 中使用单值容器，应该没问题。

这是您的 Group 的外观，

struct Group: Decodable {
    var name: String!
    var groups: GroupData

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        groups = try container.decode(GroupData.self)
    }
}

注意，你的json本身是错误的，我已经格式化了，应该是这样的，

let jsonString = "{\"groupName\":{\"groupA\":{\"fields\":{\"fieldA\":\"valueA\",\"fieldB\":\"valueB\"},\"letters\":{\"letterA\":\"A\"}},\"groupB\":{\"fields\":{\"fieldC\":\"valueC\",\"fieldD\":\"valueD\"},\"letters\":{\"letterB\":\"B\"}}}}"