@已发布属性未从嵌套视图模型更新视图-SwiftUI
当视图模型嵌套在另一个视图模型中时,我不确定为什么视图没有得到更新。我的理解是,子视图模型中的@Published属性将触发父视图模型中的更改,从而将更改推送到UI 这是子视图模型:@已发布属性未从嵌套视图模型更新视图-SwiftUI,swiftui,Swiftui,当视图模型嵌套在另一个视图模型中时,我不确定为什么视图没有得到更新。我的理解是,子视图模型中的@Published属性将触发父视图模型中的更改,从而将更改推送到UI 这是子视图模型: class FilterViewModel : ObservableObject, Identifiable { var id = UUID().uuidString var name = "" var backgroundColour = ""
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
}
}
但是,我想尝试一系列过滤器视图模型:
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视图
struct ContentView: View {
@ObservedObject var filterListVM = FilterListViewModel()
Button(action: { filterListVM[0].changeSelected()}, label: {
Text(filterListVM[0].name)
.background(Color(filterListVM[0].backgroundColour))
})
}
最简单的方法是将
filtervewmodel
定义为结构。因此,它是一种值类型。值更改时,结构也会更改。然后,ListViewModel会触发一个更改
struct FilterViewModel : Identifiable {
var id = UUID().uuidString
var name = ""
var backgroundColour = ""
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)
}
mutating func changeSelected() {
self.selected = !self.selected
}
}
struct FilterViewModel:可识别{
var id=UUID().uuistring
var name=“”
var backgroundcolor=“”
所选变量=false
private var cancelables=Set()
init(名称:String){
self.name=名称
$selected.map{uu}in
自选“橙色”:“浅灰色”
}
.分配(给:\.背景颜色,在:self上)
.store(在:&可取消项中)
}
mutating func changeSelected(){
self.selected=!self.selected
}
}
另一种解决方案是对子模型使用单独的视图:
struct FilterView: View {
@ObservedObject var filterVM: FilterViewModel
var body: some View {
Button(action: { filterVM.changeSelected()}, label: {
Text(filterVM.name)
.background(Color(filterVM.backgroundColour))
})
}
}
所以在父视图中,现在我们可以将其用作
struct ContentView: View {
@ObservedObject var filterListVM = FilterListViewModel()
// ...
FilterView(filterVM: filterListVM[0])
}
谢谢,这很有效。您知道为什么这样做比通过其父级引用子VM更有效吗?ObservedObject只观察到一个级别发布的值发生变化,在您的情况下,当内部子属性发生变化时,对子级的引用不会发生变化。
struct ContentView: View {
@ObservedObject var filterListVM = FilterListViewModel()
// ...
FilterView(filterVM: filterListVM[0])
}