Is this approach is an Anti-Pattern? - Flutter - flutter

Question

strong textI'm implementing a contacts list search bar, where the user can search & select some contacts, but I need the selected contacts to be shown as selected while the user is still searching.
I achieved this by modifying the original list and the duplicate list which used in the searching process at the same time.
is this an Anti-Pattern and is there a better way to do it?
Here's what I'm doing with the search query:
void searchContacts([String? name]) {
if (name == null || name.isEmpty) {
searchedList.clear();
addAllContactsToSearchList();
return;
} else {
searchedList.clear();
originalContactsList!.forEach((contact) {
if (contact.name.toLowerCase().contains(name.toLowerCase())) {
searchedList.clear();
searchedList.add(contact);
return;
} else {
return;
}
});
return;
}
}
and here's the code for selecting a contact:
void _onChange(bool value, int index) {
final selectedContact = searchedList[index].copyWith(isSelected: value);
searchedList.removeAt(index);
setState(() {
searchedList.insert(index, selectedContact);
notifier.originalContactsList = notifier.originalContactsList!.map((e) {
if (e.number == selectedContact.number) {
return selectedContact;
} else {
return e;
}
}).toList();
});}
This is expected behavior: gif

Answer 1

Some assumptions I'm making is that (1) each contact has a unique identifier that isn't just a name, and (2) you don't need the selected contacts to be shown in the same list as a search with a different query (if you search H, select Hasan, then search Ha, you expect it to still show up as selected on the next page, but if you search He, Hasan shouldn't shouldn't be on that next list.
The best way to do this is to have one constant list, and one list with results:
Set<String> selectedContactIds = {};
List<Contact> searchedList = [];
void _onChange(bool value, int index) {
final clickedContact = searchedList[index];
bool itemAlreadySelected = selectedContactIds.contains(clickedContact.userID);
setState({
if(itemAlreadySelected) {
selectedContactIds.remove(clickedContact.userID);
} else {
selectedContactIds.add(clickedContact.userID);
}
});
}
Now once you set state, your ListView should be updating the appearance of selected objects by checking if it's selected the same way that the _onChange function is checking if the item was already selected, which was:
bool itemAlreadySelected = selectedContactIds.contains(clickedContact.userID);
And this way, you don't have a whole class for contacts with a dedicated isSelected member. You wouldn't want that anyways because you're only selecting contacts for very specific case by case uses. Hopefully this helps!