[英]persistent value in a picker changing views in SwiftUI
我不明白如何在 SwiftUI 中实现一个简单的选择器,该选择器显示一个值列表,该列表保留在不同视图之间切换的选定值。 顺便说一句,我可以使用选定的值通过组合框架更新 Model。
这是代码,但onAppear{}
/ onDisappear{}
没有按预期工作:
struct CompanyView: View {
@ObservedObject var dataManager: DataManager = DataManager.shared
@State var selTipoAzienda = 0
var body: some View {
VStack {
companyPhoto
Text("Company view")
Form {
Picker(selection: $selTipoAzienda, label: Text("Tipo Azienda")) {
ForEach(0 ..< self.dataManager.company.tipoAziendaList.count) {
Text(self.dataManager.company.tipoAziendaList[$0])
}
}
}
Button(action: {self.dataManager.cambiaTipoAzienda(tipoAzienda: self.dataManager.company.tipoAziendaList[self.selTipoAzienda]) }) {
Image(systemName: "info.circle.fill")
.font(Font.system(size: 28))
.padding(.horizontal, 16)
}
}
// .onAppear{
// self.selTipoAzienda = self.dataManager.company.tipoAziendaList.firstIndex(of: self.dataManager.company.tipoAzienda) ?? 0
// }
// .onDisappear{
// self.dataManager.cambiaTipoAzienda(tipoAzienda: self.dataManager.company.tipoAziendaList[self.selTipoAzienda])
// }
}
我认为 binding 和 didSet 将是答案,但我不知道它们必须如何实现
提供的代码不可编译/不可测试,因此下面仅显示一种方法(另请参见内联注释)
struct CompanyView: View {
@ObservedObject var dataManager: DataManager = DataManager.shared
@State var selTipoAzienda: Int
init() {
// set up initial value from persistent data manager
_selTipoAzienda = State(initialValue: self.dataManager.company.tipoAziendaList.firstIndex(of: self.dataManager.company.tipoAzienda) ?? 0)
}
var body: some View {
// inline proxy binding to intercept Picker changes
let boundSelTipoAzienda = Binding(get: { self.selTipoAzienda }, set: {
self.selTipoAzienda = $0
// store selected value into data manager
self.dataManager.cambiaTipoAzienda(tipoAzienda: self.dataManager.company.tipoAziendaList[$0])
})
return VStack {
companyPhoto
Text("Company view")
Form {
Picker(selection: boundSelTipoAzienda, label: Text("Tipo Azienda")) {
ForEach(0 ..< self.dataManager.company.tipoAziendaList.count) {
Text(self.dataManager.company.tipoAziendaList[$0])
}
}
}
Button(action: {self.dataManager.cambiaTipoAzienda(tipoAzienda: self.dataManager.company.tipoAziendaList[self.selTipoAzienda]) }) {
Image(systemName: "info.circle.fill")
.font(Font.system(size: 28))
.padding(.horizontal, 16)
}
}
}
}
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