SwiftUI Timer.publish 导致整个屏幕刷新

Question

GIF of Entire Screen Refreshing

我目前正在学习 combine 和 MVVM。我的问题是当我尝试使用 timer.publish 时，最终我要创建一个停止按钮，它会导致整个屏幕刷新，而不是刷新我拥有的 .onReceive 文本。

我希望有人可以提供一些见解，让我了解我如何错误地使用发布者和观察者。

查看：

import SwiftUI
import Combine

struct ApptCardView: View {

    @ObservedObject var apptCardVM: ApptCardViewModel
    @State var currentDate = Date()
    let timer = Timer.publish(every: 1, on: .main, in: .common).autoconnect()

    var body: some View {
        VStack {
            Text("\(currentDate)")
                .onReceive(timer) { input in
                    self.currentDate = input
                   }
            Picker("Seizure Type", selection: $apptCardVM.typeIndex) {
            ForEach(0..<apptCardVM.typeChoice.count) {
                Text(self.apptCardVM.typeChoice[[=11=]])
            }
        }.pickerStyle(SegmentedPickerStyle())

        }

    }
}

查看模型：

import Foundation
import Combine


class ApptCardViewModel: ObservableObject, Identifiable {

    @Published var appt: ApptEvent
    @Published var typeChoice = ["Quick", "Long", "FullService"]
    @Published var typeIndex: Int = 0



    private var cancellables = Set<AnyCancellable>()

    init(appt: ApptEvent) {
        self.appt = appt
    }

}

Answer 1

如果你只想刷新body的一部分，那么将那部分分开到专用的子视图中，例如：

struct ApptCardView: View {

    @ObservedObject var apptCardVM: ApptCardViewModel

    var body: some View {
        VStack {
            CurrentDateView()  // << here !!

            Picker("Seizure Type", selection: $apptCardVM.typeIndex) {
            ForEach(0..<apptCardVM.typeChoice.count) {
                Text(self.apptCardVM.typeChoice[[=10=]])
            }
        }.pickerStyle(SegmentedPickerStyle())

        }

    }
}

struct CurrentDateView: View {
    @State private var currentDate = Date()
    let timer = Timer.publish(every: 1, on: .main, in: .common).autoconnect()
    var body: some View {
        Text("\(currentDate)")
            .onReceive(timer) { input in
                self.currentDate = input // << refresh only own body !!
        }
    }
}

SwiftUI Timer.publish 导致整个屏幕刷新

SwiftUI Timer.publish causing whole screen to refresh

swiftui

swiftui-environment