[英]Decode JSON object to plain String in Swift
This is a follow-up question to that question I asked a few days ago, reading it beforehand is not strictly necessary though.这是我几天前问的那个问题的后续问题,不过,事先阅读它并不是绝对必要的。
I have an API endpoint /common
, returning JSON data in that form: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
}]
}
}
In further code snippets, it is assumed that this response is stored as a String
in the variable rawApiResponse
.在进一步的代码片段中,假设此响应作为
String
存储在变量rawApiResponse
。
My aim is to decode that to according Swift struct
s:我的目标是根据 Swift
struct
s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"
}
}
Thanks to the answer in my original question, I can now decode Player
s and Game
s successfully, but only when the response String
I use is the inner array, eg
:感谢我原来问题中的答案,我现在可以成功解码
Player
s 和Game
s,但只有当我使用的响应String
是内部数组时, eg
:
let playersResponse = """
[
{
"id": 1,
"name": "John Doe"
},
{
"id": 15,
"name": "Jessica Thump"
}
]
"""
let players = try! JSONDecoder().decode([Player].self, from: playersResponse.data(using: .utf8)!)
How can I extract only the JSON "players"
array from /common
's API response, so that I can feed it afterwards to a JSON decoder for my Player
s?如何仅从
/common
的 API 响应中提取 JSON "players"
数组,以便之后可以将其提供给我的Player
的 JSON 解码Player
?
Please note that I can't use (or that's at least what I think) the "usual" Decodable
way of making a super- Struct
because I need players
to be decoded before games
(that was the topic of the original question).请注意,我不能使用(或者至少我认为是这样)制作超级
Struct
的“通常”可Decodable
方式,因为我需要在games
前对players
进行解码(这是原始问题的主题)。 So, this doesn't work: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)!)
I looked into how to convert a JSON string to a dictionary but that only partially helped:我研究了如何将 JSON 字符串转换为字典,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"]!!
If I dump playersRaw
, it looks like what I want, but I have no clue how to cast it to Data
to pass it to my JSONDecoder
, as type(of: playersRaw)
is __NSArrayM
.如果我转储
playersRaw
,它看起来像我想要的,但我不知道如何将它转换为Data
以将它传递给我的JSONDecoder
,因为type(of: playersRaw)
是__NSArrayM
。
I feel like I'm not doing things the way they should be done, so if you have a more "Swifty" solution to the general problem (and not specifically to how to extract a subset of the JSON data), it would be even nicer!我觉得我没有按照他们应该做的方式做事,所以如果你有一个更“Swifty”的解决方案来解决一般问题(而不是专门针对如何提取 JSON 数据的子集),它甚至更好!
You can make that happen by implementing the decoding yourself in ApiData
and searching for each player id in the players
array:您可以通过在
ApiData
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: { $0.id == playerId1 }),
let player2 = players.first(where: { $0.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
}
It's a little ugly, but in the end you can use it like this:有点难看,但最后你可以这样使用它:
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)
}
You just need to provide a root structure and get its data players.您只需要提供一个根结构并获取其数据播放器。 No need to decode the values you don't want:
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)
}
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