SwiftUI @State在教程中使用

Question

当我尝试教程的animating-views-and-transitions部分时，当我下载整个项目并单击“海拔”，“心率”和“步速”按钮时。它不会像教程中那样改变画布。相反，它保留了颜色，但“胶囊”的位置有所变化。

我猜@State可能不太正确，但是我不知道如何解决它。部分代码如下所示。整个项目为here

HikeDetail.swift此视图将@State传递给HikeGraph，HikeGraph将图片更改为该@State

struct HikeDetail: View {
    let hike: Hike
    @State var dataToShow = \Hike.Observation.elevation
    
    var buttons = [
        ("Elevation", \Hike.Observation.elevation),
        ("Heart Rate", \Hike.Observation.heartRate),
        ("Pace", \Hike.Observation.pace),
    ]
    
    var body: some View {
        return VStack {
            HikeGraph(hike: hike, path: dataToShow)
                .frame(height: 200)
            
            HStack(spacing: 25) {
                ForEach(buttons, id: \.0) { value in
                    Button(action: {
                        self.dataToShow = value.1
                    }) {
                        Text(value.0)
                            .font(.system(size: 15))
                            .foregroundColor(value.1 == self.dataToShow
                                ? Color.gray
                                : Color.accentColor)
                            .animation(nil)
                    }
                }
            }
        }
    }
}

HikeGraph.swift。它应该随着HikeDetail传递的路径而改变颜色。但这不是

struct HikeGraph: View {
    var hike: Hike
    var path: KeyPath<Hike.Observation, Range<Double>>
    
    var color: Color {
        switch path {
        case \.elevation:
            return .gray
        case \.heartRate:
            return Color(hue: 0, saturation: 0.5, brightness: 0.7)
        case \.pace:
            return Color(hue: 0.7, saturation: 0.4, brightness: 0.7)
        default:
            return .black
        }
    }
    
    var body: some View {
        let data = hike.observations
        let overallRange = rangeOfRanges(data.lazy.map { $0[keyPath: self.path] })
        let maxMagnitude = data.map { magnitude(of: $0[keyPath: path]) }.max()!
        let heightRatio = (1 - CGFloat(maxMagnitude / magnitude(of: overallRange))) / 2

        return GeometryReader { proxy in
            HStack(alignment: .bottom, spacing: proxy.size.width / 120) {
                ForEach(data.indices) { index in
                    GraphCapsule(
                        index: index,
                        height: proxy.size.height,
                        range: data[index][keyPath: self.path],
                        overallRange: overallRange)
                    .colorMultiply(self.color)
                    .transition(.slide)
                    .animation(.ripple(index: index))
                }
                .offset(x: 0, y: proxy.size.height * heightRatio)
            }
        }
    }
}