Dart List doesnt get updated with forEach loop - flutter

Question

I am using this package to retrieve device's contacts. The lib retrieve 427 contacts and I want to loop the whole list so that I can create another list and send it to the back-end. The problem is looping does not work this the function return before looping is completed.
Here the function I use:
Future<QueryResult> uploadContacts() async {
final List<Contact> rawContacts =
(await ContactsService.getContacts(withThumbnails: false)).toList();
List<ContactInput> contactsListInput;
print('contactsListInput length: ${rawContacts.length}');
rawContacts.forEach((contact) {
print('contact: $contact'); //PRINTED JUST ONCE
//Contact can have more than 1 number. We need them all
contact.phones.forEach((phone) {
final contactInput =
ContactInput(name: contact.displayName, phone: phone.value);
contactsListInput.add(contactInput);
});
});
print('contactsListInput length: ${contactsListInput.length}'); //NEVER PRINT ANYTHING
final ContactsListInput input =
ContactsListInput(contacts: contactsListInput);
final MutationOptions _options = MutationOptions(
document: SyncContactsMutation().document,
variables: SyncContactsArguments(input: input).toJson());
return client.mutate(_options);
}
I have also tried using for loop and the same thing happened.
for (int i = 0; i < rawContacts.length; i++) {
final contact = rawContacts[i];
final contactInput =
ContactInput(name: contact.displayName, phone: contact.phones.first.value);
contactsListInput.add(contactInput);
}
print('contactsListInput length: ${contactsListInput.length}'); //NEVER CALLED
And I also tried Future.forEach
await Future.forEach(rawContacts, (contact) async {
print('contact: $contact');
//Since contact can have more than one number we loop them too.
await Future.forEach(contact.phones, (phone) async {
final contactInput =
ContactInput(name: contact.displayName, phone: phone.value);
contactsListInput.add(contactInput);
});
});
How to fix this? Any help will be much appreciated.

Answer 1

I have fixed it as
Future<QueryResult> uploadContacts() async {
final Iterable<Contact> rawContacts =
(await ContactsService.getContacts(withThumbnails: false));
final Iterable<ContactInput> contacts = rawContacts.expand((contact) => contact.phones.map(
(phone) =>
ContactInput(name: contact.displayName, phone: phone.value)));
final input = ContactsListInput(contacts: contacts);
final MutationOptions _options = MutationOptions(
document: SyncContactsMutation().document,
variables: SyncContactsArguments(input: input).toJson());
return client.mutate(_options);
}
Credit goes to #pskink and #loganrussell48

Answer 2

You should use it as a dynamic type object. Try something like this:
(event.snapshot.value as dynamic).forEach()
Try and see if it works.