struct ContentView: View {
   @Environment(ApplicationData.self) private var appData
   @State private var searchTerm: String = ""

   var body: some View {
      NavigationStack {
         List(appData.filteredItems) { book in
            CellBook(book: book)
         }
         .navigationTitle(Text("Books"))
      }
      .searchable(text: $searchTerm, prompt: Text("Insert title"))
      .onSubmit(of: .search) { performSearch() }
      .onChange(of: searchTerm, initial: false) { old, value in
         if value.isEmpty {
            performSearch()
         }
      }
   }
   func performSearch() {
      let search = searchTerm.trimmingCharacters(in: .whitespaces)
      appData.filterValues(search: search)
   }
}