Swift Json 将嵌套数组/字典解码为平面模型

问题描述

我正在尝试在 Swift 中将以下 json 对象解码为我的 User 模型。

我的问题是从 _id 数组中解码值 token 和 tokens，其中数组中的第一个标记包含我想解码为 User.tokenId 和 User 的值.token。

我试图将值直接提取/映射到我的用户模型结构中，而我的用户模型中没有另一个嵌套结构（例如 struct Token { var id: String,var token: String } ）

let json = """
    {
        "currentLocation": {
            "latitude": 0,"longitude": 0
        },"profileImageUrl": "","bio": "","_id": "601453e4aae564fc19075b68","username": "johnsmith","name": "john","email": "[e-mail]","keywords": ["word","weds"],"tokens": [
            {
                "_id": "213453e4aae564fcqu775b69","token": "eyJhbGciOiJIUzqoNiIsInR5cCI6IkpXVCJ9.eyJfaWQiOiI2MDE0NTNlNGFhZTU2NGZjMTkwNzViNjgiLCJpYXQiOjE2MTE5NDQ5MzIsImV4cCI6MTYxMjM3NjkzMn0.PbTsA3B0MAfcVvEF1UAMhUXFiqIL1FcxvFGgMTZ5HCk"
            }
        ],"createdAt": "2021-01-29T18:28:52.845Z","updatedAt": "2021-01-29T18:28:52.883Z"
    }
    """.data(using: .utf8)!


struct User: Codable {
    var latitude: Double 
    var longitude: Double 
    var profileImageUrl: String 
    var bio: String 
    var userId: String 
    var username: String
    var name: String
    var email: String
    var keywords: [String]
    var tokenId: String
    var token: String
    var createdAt: Date
    var updatedAt: Date
    
    private enum UserKeys: String,CodingKey {
        case currentLocation
        case profileImageUrl
        case bio
        case userId = "_id"
        case username
        case name
        case email
        case keywords
        case tokens
        case createdAt
        case updatedAt
    }
    
    private enum CurrentLocationKeys: String,CodingKey { 
        case latitude
        case longitude
    }
    
    private enum TokenKeys: String,CodingKey {
        case tokenId = "_id"
        case token
    }
    
    init(from decoder: Decoder) throws {
        
        let userContainer = try decoder.container(keyedBy: UserKeys.self)
              let currentLocationContainer = try userContainer.nestedContainer(keyedBy: CurrentLocationKeys.self,forKey: .currentLocation) 
              self.latitude = try currentLocationContainer.decode(Double.self,forKey: .latitude)
              self.longitude = try currentLocationContainer.decode(Double.self,forKey: .longitude)
            self.profileImageUrl = try userContainer.decode(String.self,forKey: .profileImageUrl)
            self.bio = try userContainer.decode(String.self,forKey: .bio)
            self.userId = try userContainer.decode(String.self,forKey: .userId)
            self.username = try userContainer.decode(String.self,forKey: .username)
            self.name = try userContainer.decode(String.self,forKey: .name)
            self.email = try userContainer.decode(String.self,forKey: .email)
            self.keywords = try userContainer.decode([String].self,forKey: .keywords)
              let tokensContainer = try userContainer.nestedContainer(keyedBy: TokenKeys.self,forKey: .tokens)
              self.tokenId = try tokensContainer.decode(String.self,forKey: .tokenId)
              self.token = try tokensContainer.decode(String.self,forKey: .token)
            self.createdAt = try userContainer.decode(Date.self,forKey: .createdAt)
            self.updatedAt = try userContainer.decode(Date.self,forKey: .updatedAt)
    }
}

let user = try! decoder.decode(User.self,from: json)

解决方法

首先，我假设您的 decoder 具有适当的日期解码策略，能够将 ISO8601 字符串解码为 Date。

token 字典的封闭容器是一个数组。您必须插入中间 nestedUnkeyedContainer

...
var arrayContainer = try userContainer.nestedUnkeyedContainer(forKey: .tokens)
let tokensContainer = try arrayContainer.nestedContainer(keyedBy: TokenKeys.self)
self.tokenId = try tokensContainer.decode(String.self,forKey: .tokenId)
self.token = try tokensContainer.decode(String.self,forKey: .token)
...

将 JSON 解码为多个结构体的代码要少得多