Question

问题底部的解决方法

我认为SwiftUI应该在数据依赖于更改时自动更新视图。但是，以下代码中没有发生这种情况：

首先，我做一个简单的BindableObject

import SwiftUI
import Combine

class Example: BindableObject {
    var didChange = PassthroughSubject<Void, Never>()

    var test = 1 {
        didSet {
            didChange.send(())
        }
    }
}

然后是应用程序的根视图：

struct BindTest : View {
    @Binding var test: Example
    var body: some View {
        PresentationButton(destination: BindChange(test: $test)) {
            ForEach(0..<test.test) { index in
                Text("Invalidate Me! \(index)")
            }
        }
    }
}

最后是我更改BindableObject的值的视图：

struct BindChange : View {
    @Binding var test: Example
    @Environment(\.isPresented) var isPresented
    var body: some View {
        Button(action: act) {
            Text("Return")
        }
    }

    func act() {
        test.test = 2
        isPresented?.value = false
    }
}

点击返回按钮时，应该有两个Text View实例-但只有1个。我在做什么错了？

还值得注意的是：如果我将@Binding更改为@EnvironmentObject，则在您点击产生此错误的按钮时，程序只会崩溃：

线程1：EXC_BAD_INSTRUCTION（代码= EXC_I386_INVOP，子代码= 0x0）

下面的完整代码：

import SwiftUI
import Combine

class Example: BindableObject {
    var didChange = PassthroughSubject<Example, Never>()

    var test = 1 {
        didSet {
            didChange.send(self)
        }
    }

    static let `default` = {
        return Example()
    }()
}
//Root View
struct BindTest : View {
    @EnvironmentObject var test: Example
    var body: some View {
        PresentationButton(destination: BindChange()) {
            ForEach(0..<test.test) { t in
                Text("Invalidate Me! \(t)")
            }
        }
    }
}
//View that changes the value of @Binding / @EnvironmentObject
struct BindChange : View {
    @EnvironmentObject var test: Example
    @Environment(\.isPresented) var isPresented
    var body: some View {
        Button(action: act) {
            Text("Return")
        }
    }

    func act() {
        test.test = 2
        isPresented?.value = false
    }
}

#if DEBUG
struct ContentView_Previews : PreviewProvider {

    static var previews: some View {
        //ContentView().environmentObject(EntryStore())
        BindTest().environmentObject(Example())
    }
}
#endif

编辑2：此时的帖子有点混乱，但是EnvironmentObject的崩溃似乎与PresentationButton的问题有关

通过将NavigationButton放在NavigationView中，以下代码将产生正确的结果-当List更改时，test.test无效：

//Root View
struct BindTest : View {
    @EnvironmentObject var test: Example
    var body: some View {
        NavigationView {
            NavigationButton(destination: BindChange()) {
                ForEach(0..<test.test) { t in
                    Text("Functional Button #\(t)")
                }
            }
        }
    }
}

无效列表SwiftUI

问题底部的解决方法

0 个答案: