SwiftUI：检测@State变量何时在其@Binding中发生变化

Question

我想知道如何改变不同 View 的值。下面是我的主要观点的实现：

import SwiftUI
import Combine

struct ContentView: View {
    @State private var isPresented: Bool = false
    
    @State private var textToProces = "" {
        didSet{
            print("text: oldValue=\(oldValue) newValue=\(textToProces)")

        }
    }
    var body: some View {
       
        ZStack{
            VStack{
                Button("Show Alert"){
                    self.isPresented = true
                }.background(Color.blue)
            }
            ItemsAlertView(isShown: $isPresented, textToProcess: $textToProces)
        }
    }
}

在这个视图中，我正在尝试更改 textToProces 变量：

struct AnotherView: View {
    
    @Binding var isShown: Bool
    @Binding var textToProcess: String

    var title: String = "Add Item"
    let screenSize = UIScreen.main.bounds
    
    var body: some View {
        VStack {
            Button(action: {
                self.textToProcess = "New text"
                self.isShown = false
            }, label: {
                Text("dissmis")
            })
            Text(self.textToProcess)
        }
        .background(Color.red)
        .offset(y: isShown ? 0 : screenSize.height)
    }
}

当我更改此行 self.textToProcess = "New text" 上的值时，主视图中的 textToProcess 永远不会收到更改通知。你们知道我该怎么做才能在主视图中收到更改通知吗？

非常感谢你的帮助

Answer 1

您必须使用 onChange 修饰符来跟踪对 textToProces 的更改。

import SwiftUI
import Combine

struct ContentView: View {
    @State private var isPresented: Bool = false
    
    @State private var textToProces = ""

    var body: some View {
       
        ZStack{
            VStack{
                Button("Show Alert"){
                    self.isPresented = true
                }.background(Color.blue)
            }
            ItemsAlertView(isShown: $isPresented, textToProcess: $textToProces)
        }
        .onChange(of: textToProces) { value in
            print("text: \(value)")
        }
    }
}

SwiftUI：检测@State变量何时在其@Binding中发生变化

SwiftUI: detecting when @State variable has change in their @Binding

ios

swiftui

xcode12

swiftui-state