对要保存在 AppStorage 中的结构进行编码

Question

目前正在尝试在 swiftUI 中构建我的第一个应用程序。我认为最简单的部分会成为一场噩梦......在 AppStorage 中保存一个结构，以便在重新启动应用程序时可用

我有两个结构要保存。第一个是针对玩家的，我已经实现了

RawRepresentable

struct Player: Codable, Identifiable {
    let id: Int
    let name: String
    let gamePlayed: Int
    let bestScore: Int
    let nbrGameWon: Int
    let nbrGameLost: Int
    let totalScore: Int?

}

typealias PlayerList = [Player]
extension PlayerList: RawRepresentable {
    public init?(rawValue: String) {
        guard let data = rawValue.data(using: .utf8),
            let result = try? JSONDecoder().decode(PlayerList.self, from: data)
        else {
            return nil
        }
        self = result
    }

    public var rawValue: String {
        guard let data = try? JSONEncoder().encode(self),
            let result = String(data: data, encoding: .utf8)
        else {
            return "[]"
        }
        return result
    }
}

在我看来这样调用：

struct AddPlayerView: View {
    @State var name: String = ""
    @State var isDisabled: Bool = false
    @State var modified: Bool = false
    @AppStorage("players") var players: PlayerList = PlayerList()
    ...
}

上面的作品，现在我还想保存当前的游戏数据，我有以下结构：

struct Game: Codable, Identifiable {
    var id: Int
    var currentPlayerIndexes: Int
    var currentRoundIndex: Int?
    var dealerIndex: Int?
    var maxRounds: Int?
    var dealResults: [Int: Array<PlayerRoundSelection>]?
    var currentLeaderIds: Array<Int>?
    var isGameInProgress: Bool?
}

extension Game: RawRepresentable {
    public init?(rawValue: String) {
        if rawValue == "" {
            // did to fix issue when calling AppStorage, but it is probably a bad idea
            self = Game(id:1, currentPlayerIndexes:1)
        }
        else {
            guard let data = rawValue.data(using: .utf8),
                let result = try? JSONDecoder().decode(Game.self, from: data)
            else {
                return nil
            }
            self = result
        }
    }

    public var rawValue: String {
        guard let data = try? JSONEncoder().encode(self),
            let result = String(data: data, encoding: .utf8)
        else {
            return ""
        }
        return result
    }
}

一旦我尝试修改结构，它就会调用

rawValue

并且编码失败，并显示以下内容：

error: warning: couldn't get required object pointer (substituting NULL): Couldn't load 'self' because its value couldn't be evaluated

error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=2, address=0x7ffee49bbff8).

这里是访问结构体的部分代码：

struct SelectPlayersView: View {
    @AppStorage("currentGame") var currentGame: Game = Game(rawValue: "")!
    ....
NavigationLink(
                    destination: SelectModeTypeView(), tag: 2, selection: self.$selection) {
                    ActionButtonView(text:"Next", disabled: self.$isDisabled, buttonAction: {
                        var currentPlayers = Array<Int>()
                        self.players.forEach({ player in
                            if selectedPlayers.contains(player.id) {
                                currentPlayers.insert(player.id, at: currentPlayers.count)
                            }
                        })
    // This used to be a list of indexes, but for testing only using a single index
    self.currentGame.currentPlayerIndexes = 6
                        self.selection = 2
                    })
...

我在这里找到了编码的代码：https://lostmoa.com/blog/SaveCustomCodableTypesInAppStorageOrSceneStorage/

我的理解是，使用编码中的

self

，它会生成无限循环，从而导致访问错误。

我真的不知道如何正确编码，任何帮助，链接将不胜感激

Answer 1

我也遇到了同样的问题，我想在这里分享我的经验。

我最终发现，与 RawRepresentable 结合使用时，显然你不能依赖默认的 Codable 协议实现。 因此，当我使用 CodingKeys 等进行自己的 Codable 实现时，它起作用了！

我认为你的游戏的可编码实现会是这样的：

enum CodingKeys: CodingKey {
    case currentPlayerIndexes
    case currentRoundIndex
    // <all the other elements too>
}

init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    self.currentPlayerIndexes = try container.decode(Int.self, forKey: .currentPlayerIndexes)
    self.currentRoundIndex = try container.decode(Int.self, forKey: .currentRoundIndex)
    // <and so on>
}

func encode(to encoder: Encoder) throws {
    var container = encoder.container(keyedBy: CodingKeys.self)
    try container.encode(currentPlayerIndexes, forKey: .currentPlayerIndexes)
    try container.encode(currentRoundIndex, forKey: .currentRoundIndex)
    // <and so on>
}

然后我想知道为什么你的播放器编码/解码did工作，并发现数组的默认编码和解码（即PlayerList，即

[Player]

）工作正常。