我想知道我应该如何在下面的视图中更改@State 属性包装器 showErrorAlert
struct SettingsView: View {
@State private var shouldPresent = false
@State var showErrorAlert = false
var body: some View {
VStack {
Form {
Text("Settings")
.font(.title)
Button("Import source data") {
self.shouldPresent.toggle()
}
.sheet(isPresented: $shouldPresent) {
DocumentPicker()
}
Button("Show error alert") {
self.showErrorAlert.toggle()
}
.alert(isPresented: $showErrorAlert, content: {
Alert(title: Text("Error"))
})
}
}
}
}
来自 DocumentPicker 结构代码，以防读取所选文件失败。
struct DocumentPicker: UIViewControllerRepresentable {
func makeCoordinator() -> DocumentPicker.Coordinator {
return DocumentPicker.Coordinator(parent: self)
}
func makeUIViewController(context: UIViewControllerRepresentableContext<DocumentPicker>) -> UIDocumentPickerViewController {
let picker = UIDocumentPickerViewController(documentTypes: [String(kUTTypeJSON)], in: .import)
picker.allowsMultipleSelection = false
picker.delegate = context.coordinator
return picker
}
func updateUIViewController(_ uiViewController: UIDocumentPickerViewController, context: UIViewControllerRepresentableContext<DocumentPicker>) {
}
class Coordinator: NSObject, UIDocumentPickerDelegate {
var myParent: DocumentPicker
init(parent: DocumentPicker) {
myParent = parent
}
func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
let fileURL = urls.first!
do {
let origFile = try String(contentsOf: fileURL)
//File processing will be here
} catch let error {
print(error)
}
}
}
}
我的意思是如何将属性包装器值设置为 true 以显示警报。我应该改用@ObservedObject 还是@EnvironmentObject？谢谢。