Removing elements from a list where a nested value is null or empty in dart and flutter-CodePudding

I want to get my contacts from my phone and save them into firebase. The following code works if all I wanted to do is save the contact name, mainly because the name cannot be empty in the phone but a problem arises when the nested value contact.phones is null or empty (shown below as "//works if I remove this").

Currently, if the phone field is empty, it throws a "StateError (Bad state: No element)" error.

Also, note that contacts.phone (result.phones after the attempt to remove the elements) is a list so I need to grab the first one.

I have tried to remove those elements from the list but that also sufferers from the same problem, the code to remove the empty phone fields fails for the same reason on this line.

if (!["", null, false, 0].contains(contact.phones?.first))

What is the correct way to remove elements from a list where the nested element is null or empty?



import '../../backend/backend.dart';
import '../../flutter_flow/flutter_flow_theme.dart';
import '../../flutter_flow/flutter_flow_util.dart';
import 'index.dart'; // Imports other custom actions
import 'package:flutter/material.dart';

import 'package:contacts_service/contacts_service.dart';

Future syncContactstoFirebase(String? userID) async {
  List<Contact> contacts = await ContactsService.getContacts();
List result = [];


for (var contact in contacts) {
  if (!["", null, false, 0].contains(contact.phones?.first)) {
    result.add(contact);
  }
}
  final instance = FirebaseFirestore.instance;

  CollectionReference collection =
      instance.collection('users').doc(userID).collection('contacts');

  late Map<String, dynamic> data;
  if (result != null)
    data = {
      'contacts': contacts
          .map((k) => {
                'name ': k.displayName,
                  'phone': k.phones?.first.value //works if I remove this
                    .toString()
                    .replaceAll(new RegExp(r"\s\b|\b\s"), "")
                    .replaceAll(new RegExp(r'[^\w\s] '), '')
              })
          .toList(),
    };

  return collection
      .doc()
      .set(data)
      .then((value) => print("Contacts Updated"))
      .catchError((error) => print("Failed to update Contacts: $error"));
}

CodePudding user response：

I'm not entirely sure, but I believe you would want to replace it with

if (!["", null, false, 0].contains(contact.phones?.firstOrNull))

To use firstOrNull you need

import 'package:collection/collection.dart';

CodePudding user response：

I'm not sure if I understood your issue correctly but if you want to remove all contacts with null or empty phones from your contacts list, the bellow line of code should do the trick:

 contacts.removeWhere(
    (element) => element.phones == null || element.phones!.isEmpty);