swiftui - @Published 属性不从嵌套 View 模型更新 View - SwiftUI

Question

当我有一个嵌套在另一个 View 模型中的 View 模型时，我不确定为什么我的 View 没有得到更新。我的理解是， subview 模型中的 @Published 属性会触发父 View 模型的更改，从而将更改推送到 UI。
这是 subview 模型:

class FilterViewModel : ObservableObject, Identifiable {

    var id = UUID().uuidString
    var name  = ""
    var backgroundColour = ""
    @Published var selected = false

    private var cancellables = Set<AnyCancellable>()

    init(name: String){
        self.name = name
    
        $selected.map { _ in
            self.selected ? "Orange" : "LightGray"
        }
        .assign(to: \.backgroundColour, on: self)
        .store(in: &cancellables)
     }

    func changeSelected() {
    
        self.selected = !self.selected
    }
}

以下按预期工作，单击按钮后，背景颜色会发生变化。

struct ContentView: View {

    @ObservedObject var filterVM = FilterViewModel(name: "A")


    Button(action: { filterVM.changeSelected()}, label: {
        Text(filterVM.name)
            .background(Color(filterVM.backgroundColour))
    })
}

但是，我想要一组过滤器 View 模型，所以尝试过:

class FilterListViewModel: ObservableObject {

    @Published var filtersVMS = [FilterViewModel]()

    init(){
        filtersVMS = [
            FilterViewModel(name: "A"),
            FilterViewModel(name: "B"),
            FilterViewModel(name: "C"),
            FilterViewModel(name: "D")
        ]
    }
}

但是，单击按钮时不会更新以下 View

struct ContentView: View {

    @ObservedObject var filterListVM = FilterListViewModel()

    Button(action: { filterListVM[0].changeSelected()}, label: {
        Text(filterListVM[0].name)
            .background(Color(filterListVM[0].backgroundColour))
    })
}

Answer 1

替代解决方案是为您的子模型使用分离 View :

struct FilterView: View {
    @ObservedObject var filterVM: FilterViewModel

    var body: some View {
      Button(action: { filterVM.changeSelected()}, label: {
        Text(filterVM.name)
            .background(Color(filterVM.backgroundColour))
      })
    }
}

所以现在在父 View 中我们可以将它用作

struct ContentView: View {

    @ObservedObject var filterListVM = FilterListViewModel()

    // ...

    FilterView(filterVM: filterListVM[0])
}