SwiftUI 绑定到父视图重新渲染子视图 [英] SwiftUI Binding to parent view re-renders child view

问题描述

我有一个子视图，它从父视图获得了一个绑定，它控制着应用程序的侧边栏菜单.当我单击按钮切换 showSidebar 并打开菜单时，我的 vm 被重新创建，因为视图被重新渲染?有没有办法在不影响视图模型的情况下做到这一点?

struct OnboardingView:查看{@Environment (\.presentationMode) varpresentationMode@ObservedObject 私有变量 vm: OnboardingViewModel@State 私有变量过滤 = false@Binding var showSidebar: Boolinit(showSidebar: Binding) {self._showSidebar = showSidebarself.vm = OnboardingViewModel()}

解决方案

试试这个...

改变这个

@ObservedObject 私有变量 vm: OnboardingViewModel

到

@StateObject private var vm: OnboardingViewModel = OnboardingViewModel()

并摆脱

init(showSidebar: Binding) {self._showSidebar = showSidebarself.vm = OnboardingViewModel()}

<块引用>

在没有@StateObject 的视图中创建观察对象是不安全的

https://developer.apple.com/documentation/swiftui/managing-model-data-in-your-app

I have a child view that is given a binding from the parent view, which controls the app's sidebar menu. When I click the button to toggle showSidebar and open the menu, my vm is re-created because the view is re-rendered? Is there a way to do this without affecting the view model?

struct OnboardingView: View {
    @Environment (\.presentationMode) var presentationMode
    @ObservedObject private var vm: OnboardingViewModel
    @State private var filtering = false
    @Binding var showSidebar: Bool

init(showSidebar: Binding<Bool>) {
    self._showSidebar = showSidebar
    self.vm = OnboardingViewModel()
}

解决方案

Give this a try...

Change this

@ObservedObject private var vm: OnboardingViewModel

to

@StateObject private var vm: OnboardingViewModel = OnboardingViewModel()

and get rid of

init(showSidebar: Binding<Bool>) {
    self._showSidebar = showSidebar
    self.vm = OnboardingViewModel()
}

it’s unsafe to create an observed object inside a view without an @StateObject

https://developer.apple.com/documentation/swiftui/managing-model-data-in-your-app

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