Swift如何解码键为递增编号的嵌套字典结构JSON数据

方案1：直接修改模型适配字典结构（实现成本最低） #

仅需修改DataStructure中elements的属性类型，即可直接完成解码：

public class DataStructure: Codable {
    let id: Int64?
    // 把原来的[ElementStructure]? 改成 [String: ElementStructure]?
    let elements: [String: ElementStructure]?
    
    init(id: Int64?, elements: [String: ElementStructure]?) {
        self.id = id
        self.elements = elements
    }
}

解码完成后如果需要获取元素数组，直接提取字典的values即可：

let elementArray = Array(dataInstance.data.elements?.values ?? [])

方案2：自定义解码逻辑，保持原有数组类型（无需修改后续业务代码） #

如果不想改动原有调用elements数组的业务逻辑，可以通过重写DataStructure的解码初始化方法，自动把字典转换为数组存储：

public class DataStructure: Codable {
    let id: Int64?
    let elements: [ElementStructure]?
    
    enum CodingKeys: String, CodingKey {
        case id, elements
    }
    
    public required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        id = try container.decodeIfPresent(Int64.self, forKey: .id)
        // 先解码为字典结构，再提取values转为数组
        let elementsDict = try container.decodeIfPresent([String: ElementStructure].self, forKey: .elements)
        elements = elementsDict.map { Array($0.values) }
    }
    
    init(id: Int64?, elements: [ElementStructure]?) {
        self.id = id
        self.elements = elements
    }
}

该方案无需修改原有解码函数、也无需改动后续使用elements数组的逻辑。

如需保留E01/E02这类键值 #

如果业务需要用到每个元素对应的前缀键，可以给ElementStructure新增属性存储键：

public class ElementStructure: Codable {
    let key: String? // 新增字段存储E01/E02这类键
    let title: String?
    let items: [String]?
    let details: DetailStructure?
    
    init(key: String?, title: String?, items: [String]?, details: DetailStructure?) {
        self.key = key
        self.title = title
        self.items = items
        self.details = details
    }
}

对应修改DataStructure的解码逻辑，把字典的键赋值给每个元素：

public required init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    id = try container.decodeIfPresent(Int64.self, forKey: .id)
    let elementsDict = try container.decodeIfPresent([String: ElementStructure].self, forKey: .elements)
    // 遍历字典把键存入元素
    elements = elementsDict?.map { key, value in
        ElementStructure(
            key: key,
            title: value.title,
            items: value.items,
            details: value.details
        )
    }
}

内容的提问来源于stack exchange，提问作者latenightsike