将 JSON 对象解码为 Swift 中的纯字符串

Question

上下文

这是我几天前问的后续问题，不过事先阅读并不是绝对必要的。

我有一个 API 端点 /common，以这种形式返回 JSON 数据：

{
    "data":
    {
        "players": [
        {
            "id": 1,
            "name": "John Doe"
        },
        {
            "id": 15,
            "name": "Jessica Thump"
        }],
        "games": [
        {
            "name": "Tic Tac Toe",
            "playerId1": 15,
            "playerId2": 1
        }]
    }
}

在进一步的代码片段中，假定此响应作为 String 存储在变量 rawApiResponse 中。

我的目标是根据 Swift structs:

对其进行解码

struct Player: Decodable {
    var id: Int
    var name: String?
}

struct Game: Decodable {
    var name: String
    var player1: Player
    var player2: Player
    
    enum CodingKeys: String, CodingKey {
        case name
        case player1 = "playerId1"
        case player2 = "playerId2"
    }
}

多亏了我原来问题的答案，我现在可以成功解码 Players 和 Games，但只有当我使用的响应 String 是内部数组时， e.g.:

let playersResponse = """
[
    {
        "id": 1,
        "name": "John Doe"
    },
    {
        "id": 15,
        "name": "Jessica Thump"
    }
]
"""

let players = try! JSONDecoder().decode([Player].self, from: playersResponse.data(using: .utf8)!)

问题

如何从 /common 的 API 响应中仅提取 JSON "players" 数组，以便之后我可以将其提供给我的 Player 的 JSON 解码器?

请注意，我不能使用（或者至少我是这么认为的）制作超级Struct的“常规”Decodable方法，因为我需要players在 games 之前解码（这是原始问题的主题）。所以，这不起作用：

struct ApiResponse: Decodable {
    let data: ApiData
}

struct ApiData: Decodable {
    let players: [Player]
    let games: [Game]
}
let data = try! JSONDecoder().decode(ApiResponse.self, from: rawApiResponse.data(using: .utf8)!)

到目前为止我尝试了什么

我调查了但这只是部分帮助：

let json = try JSONSerialization.jsonObject(with: rawApiResponse.data(using: .utf8)!, options: .mutableContainers) as? [String:AnyObject]
let playersRaw = json!["data"]!["players"]!!

如果我转储 playersRaw，它看起来像我想要的，但我不知道如何将其转换为 Data 以将其传递给我的 JSONDecoder，因为 type(of: playersRaw) 是 __NSArrayM.

我觉得我没有按照他们应该做的方式做事，所以如果你对一般问题有更“Swifty”的解决方案 （而不是具体如何提取 JSON 数据的子集），它会更好！

Answer 1

您只需要提供一个根结构并获取它的数据播放器。无需解码您不想要的值：

struct ApiResponse: Decodable {
    let data: ApiData
}

struct ApiData: Decodable {
    let players: [Player]
    let games: [Game]
}

struct Player: Codable {
    let id: Int
    let name: String
}

struct Game: Decodable {
    var name: String
    var player1: Int
    var player2: Int
    enum CodingKeys: String, CodingKey {
        case name, player1 = "playerId1", player2 = "playerId2"
    }
}

let common = """
{
    "data":
    {
        "players": [
        {
            "id": 1,
            "name": "John Doe"
        },
        {
            "id": 15,
            "name": "Jessica Thump"
        }],
        "games": [
        {
            "name": "Tic Tac Toe",
            "playerId1": 15,
            "playerId2": 1
        }]
    }
}
"""

do {
    let players = try JSONDecoder().decode(ApiResponse.self, from: Data(common.utf8)).data.players
    print(players)  // [__lldb_expr_48.Player(id: 1, name: "John Doe"), __lldb_expr_48.Player(id: 15, name: "Jessica Thump")]
    let games = try JSONDecoder().decode(ApiResponse.self, from: Data(common.utf8)).data.games
    print(games)  // [__lldb_expr_52.Game(name: "Tic Tac Toe", player1: 15, player2: 1)]
    
    // or get the common data
    let commonData = try JSONDecoder().decode(ApiResponse.self, from: Data(common.utf8)).data
    print(commonData.players)
    print(commonData.games)
} catch {
    print(error)
}

Answer 2

您可以通过在 ApiData 中自己实现解码并在 players 数组中搜索每个玩家 ID 来实现这一点：

struct ApiResponse: Decodable {
    let data: ApiData
}

struct ApiData: Decodable {
    let players: [Player]
    var games: [Game]
    
    enum CodingKeys: String, CodingKey {
        case players
        case games
    }
    
    enum GameCodingKeys: String, CodingKey {
        case name
        case playerId1
        case playerId2
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        
        players = try container.decode([Player].self, forKey: .players)
        var gamesContainer = try container.nestedUnkeyedContainer(forKey: .games)
        games = []
        while !gamesContainer.isAtEnd {
            let gameContainer = try gamesContainer.nestedContainer(keyedBy: GameCodingKeys.self)
            let playerId1 = try gameContainer.decode(Int.self, forKey: .playerId1)
            let playerId2 = try gameContainer.decode(Int.self, forKey: .playerId2)
            guard
                let player1 = players.first(where: { [=10=].id == playerId1 }),
                let player2 = players.first(where: { [=10=].id == playerId2 })
            else { continue }
            let game = Game(
                name: try gameContainer.decode(String.self, forKey: .name),
                player1: player1,
                player2: player2
            )
            games.append(game)
        }
    }
}

struct Player: Decodable {
    var id: Int
    var name: String?
}

struct Game: Decodable {
    var name: String
    var player1: Player
    var player2: Player
}

有点丑，不过最后你可以这样用：

let decoder = JSONDecoder()
do {
    let response = try decoder.decode(ApiResponse.self, from: rawApiResponse.data(using: .utf8)!)
    let games = response.data.games
    print(games)
} catch {
    print(error)
}

将 JSON 对象解码为 Swift 中的纯字符串

Decode JSON object to plain String in Swift

json

swift

codable

decodable

上下文

问题

到目前为止我尝试了什么