如何在步进器中使用增量和减量函数，同时使用 onChange 修饰符

Question

我已经设置了audioPlayer

除了步进器的当前功能之外，我还想为 onIncrement 和 onDecrement 播放单独的声音。

该项目使用 Core Data 进行持久化。$estimatorData.qty 监听已发布的 var 我的视图模型，当数量更改时，新的数量将保存在我的视图模型中 estimatorData.save()

这是Stepper文档的链接

我正在努力思考是否其中一个初始化器适合我想要完成的任务

Stepper("", value: $estimatorData.qty.onChange { qty in
    estimatorData.save()
}, in: 0...10000)
    .frame(width: 100, height: 35)
    .offset(x: -4)
    .background(colorScheme == .dark ? Color.blue : Color.blue)
    .cornerRadius(8)

这是我的球员

func incrementTaped() {
    playSound(sound: "plus", type: "mp3")
}
 
func decrementTaped() {
    playSound(sound: "minus", type: "m4a")
}

Answer 1

问题

目前还没有结合onIncrement/onDecrement函数和value//参数bounds的初始化程序step。

您可以拥有onIncrement和onDecrement：

public init(onIncrement: (() -> Void)?, onDecrement: (() -> Void)?, onEditingChanged: @escaping (Bool) -> Void = { _ in }, @ViewBuilder label: () -> Label)

或value,bounds和step:

public init<V>(value: Binding<V>, in bounds: ClosedRange<V>, step: V.Stride = 1, onEditingChanged: @escaping (Bool) -> Void = { _ in }, @ViewBuilder label: () -> Label) where V : Strideable

解决方案

相反，您可以创建一个自定义Stepper来组合两个初始化程序：

struct CustomStepper<Label, Value>: View where Label: View, Value: Strideable {
    @Binding private var value: Value
    private let bounds: ClosedRange<Value>
    private let step: Value.Stride
    private let onIncrement: (() -> Void)?
    private let onDecrement: (() -> Void)?
    private let label: () -> Label

    @State private var previousValue: Value

    public init(
        value: Binding<Value>,
        in bounds: ClosedRange<Value>,
        step: Value.Stride = 1,
        onIncrement: (() -> Void)? = nil,
        onDecrement: (() -> Void)? = nil,
        @ViewBuilder label: @escaping () -> Label
    ) {
        self._value = value
        self.bounds = bounds
        self.step = step
        self.onIncrement = onIncrement
        self.onDecrement = onDecrement
        self.label = label
        self._previousValue = .init(initialValue: value.wrappedValue)
    }

    var body: some View {
        Stepper(
            value: $value,
            in: bounds,
            step: step,
            onEditingChanged: onEditingChanged,
            label: label
        )
    }

    func onEditingChanged(isEditing: Bool) {
        guard !isEditing else {
            previousValue = value
            return
        }
        if previousValue < value {
            onIncrement?()
        } else if previousValue > value {
            onDecrement?()
        }
    }
}

演示

struct ContentView: View {
    @State private var value = 1

    var body: some View {
        CustomStepper(value: $value, in: 1...10, onIncrement: onIncrement, onDecrement: onDecrement) {
            Text(String(value))
        }
        .onChange(of: value) {
            print("onChange value: \($0)")
        }
    }
    
    func onIncrement() {
        print("onIncrement")
    }

    func onDecrement() {
        print("onDecrement")
    }
}