当数据改变时， Picker删除选中的段

Question

我遇到了Picker的问题。当我试图改变所选段的数据状态时，它会删除它(附件)。当显示数据改变时，我如何在选择器中保持选定段(当我按下"love"按钮，所选段应保持不变)

单项选项:

struct Landmark: Identifiable, Codable, Hashable {
var id: Int
var name: String
var imageName: String
var mainImage: Image {
Image(imageName)
var liked: Bool
var popular: Bool
var recommended: Bool
}

我得到了class与数组对象:

final class ModelData: ObservableObject {
@Published var landmarks: [Landmark]
}

并尝试像这样使用picker:

struct tempSegmentControl: View {
@EnvironmentObject var modelData: ModelData
@State private var selected = ModelData().landmarks
var popularLandmarks: [Landmark] {
modelData.landmarks.filter { landmark in
(landmark.popular)
}
}
var rocommendedLandmarks: [Landmark] {
modelData.landmarks.filter { landmark in
(landmark.recommended)
}
}
var body: some View {
VStack {
Picker("Selection", selection: $selected) {
Text("All").tag(modelData.landmarks)
Text("Popular").tag(popularLandmarks)
Text("Recommended").tag(rocommendedLandmarks)
}
.pickerStyle(SegmentedPickerStyle())
.frame(width: UIScreen.main.bounds.width * 0.95)

ForEach(selected, id: .id) { land in
NavigationLink(
destination: DetailView2(landmark: land)) {
MainItem3(landmark: land)
}
}
}
}
}

删除所选段

Answer 1

selection:不能正常工作与这样的数组类型([Landmark])。

相反，您可能想要做一些简单的事情，如:

@State private var selection = 0
//...
Picker("Selection", selection: $selection) {
Text("All").tag(0)
Text("Popular").tag(1)
Text("Recommended").tag(2)

然后为稍后要迭代的数组使用computed属性:

var selected : [Landmark] {
switch selection {
case 0:
return modelData.landmarks
case 1:
//etc
}
}

你也可以用enum : Int来做这件事，如果你扩展了case，这可能会更安全一些(它会在你的computed属性中给你一个有限的集合)。