Question

仅在预览模式下出现问题是因为初始化变量之一的方式。此视图将 PlayerScore 作为参数，因为我需要知道要编辑哪个分数。它还具有 game 环境对象，其中存储了所有分数。

我做的很简单，我在 PlayerScores 的游戏数组中搜索 playerscore 的索引，以便以后对其进行修改。

预览存在的问题是，我在ScoreEntry_Previews中使用的PlayerScore显然与游戏数组中的playerScore的UUID不匹配。因此它不会呈现预览，因为var初始化失败，因为它找不到UUID。

我该如何处理？

struct ScoreEntry: View {

    @EnvironmentObject var game : Game

    @Binding var isPresented: Bool
    var playerScore: PlayerScore

    var scoreIndex: Int {
        game.playerScores.firstIndex(where: { $0.id == playerScore.id})!
    }

    var body: some View {
        HStack {
            Text("\(self.game.playerScores[self.scoreIndex].totalScore())")
        }
    }
}


struct ScoreEntry_Previews: PreviewProvider {
    static var previews: some View {
        ScoreEntry(
            isPresented: .constant(true)
            ,playerScore: PlayerScore(player: Player(name: "SomePlayer", shortName: "Steph", photoURL:"steph", color: .orange),pointsList: [1,2])
        ).environmentObject(Game())
    }
}

struct PlayerScore: Identifiable, Hashable {

    var id = UUID()
    let player: Player
    var pointsList: [Int]     

    func totalScore() -> Int {
        return pointsList.reduce(0, +)
    }

    mutating func addPoints(scoreValue: Int) {
        pointsList.append(scoreValue)
    }
}

class Game: ObservableObject {

    var players = [Player] ()
    @Published var playerScores = [PlayerScore] ()
}

Answer 1

请勿在内部自动生成id，而是使其可注入，因此您可以在“预览”中创建一个并在两个位置都注入

struct PlayerScore: Identifiable, Hashable {
    var id: UUID     // << require external

更新：实际上，以上仍然是可行的方法，但以下是不更改UUID的替代方法。

通过Xcode 11.4 / iOS 13.4测试

经过全面测试的模块代码

struct Player {
    var name: String
    var shortName: String
    var photoURL: String
    var color: Color
}

struct PlayerScore: Identifiable {

    var id = UUID()
    let player: Player
    var pointsList: [Int]

    func totalScore() -> Int {
        return pointsList.reduce(0, +)
    }

    mutating func addPoints(scoreValue: Int) {
        pointsList.append(scoreValue)
    }
}

class Game: ObservableObject {

    var players: [Player]
    @Published var playerScores: [PlayerScore]
    init(players: [Player] = [], scores: [PlayerScore] = []) {
        self.players = players
        self.playerScores = scores
    }
}

struct ScoreEntry: View {

    @EnvironmentObject var game : Game

    @Binding var isPresented: Bool
    var playerScore: PlayerScore

    var scoreIndex: Int {
        game.playerScores.firstIndex(where: { $0.id == playerScore.id})!
    }

    var body: some View {
        HStack {
            Text("\(self.game.playerScores[self.scoreIndex].totalScore())")
        }
    }
}


struct ScoreEntry_Previews: PreviewProvider {
    static var previews: some View {
        let score = PlayerScore(player: Player(name: "SomePlayer", shortName: "Steph", photoURL:"steph", color: .orange), pointsList: [1, 2])
        return ScoreEntry(isPresented: .constant(true), playerScore: score)
            .environmentObject(Game(scores: [score]))
    }
}

从环境变量初始化的var的预览问题

1 个答案: