Delayed Save On Text Edit

main.dart

import 'dart:async';
import 'package:flutter/material.dart';

void main() {
  runApp(const MainApp());
}

class DelayedTextEditingController {
  DelayedTextEditingController(
    this.onValidated,
    this.update,
    this.validate,
    String initialText,
  ) : textController = TextEditingController(text: initialText) {
    textController.addListener(() async {
      await doValidation();
      _updateFuture ??= Future.delayed(
        const Duration(seconds: 2),
        () async {
          _updateFuture = null;

          if (_lastValidValue == null || _lastUpdatedValue == _lastValidValue) {
            return;
          }
          _lastUpdatedValue = _lastValidValue;
          await update(_lastValidValue!);
        },
      );
    });
  }

  Future<void> doValidation() async {
    var text = textController.text;
    errorMessage = await validate(text);
    onValidated();
    if (errorMessage == null) {
      _lastValidValue = text;
    }
  }

  final TextEditingController textController;
  Future<void> Function(String newValue) update;
  Future<String?> Function(String value) validate;
  final void Function() onValidated;
  String? errorMessage;

  Future<void>? _updateFuture;
  String? _lastValidValue;
  String? _lastUpdatedValue;
}

class ProfileRepo {
  Future<void> updateName(String name) async {
    await Future.delayed(
        const Duration(milliseconds: 50), () => print('name updated to $name'));
  }

  Future<void> updateEmailAddress(String email) async {
    await Future.delayed(const Duration(milliseconds: 50),
        () => print('email updated to $email'));
  }
}

class Controller extends ChangeNotifier {
  Controller(this.profileRepo, String name, String emailAddress) {
    nameController = DelayedTextEditingController(
        notifyListeners,
        (s) => profileRepo.updateName(s),
        (s) async => s.isNotEmpty ? null : 'Ouch name is required',
        name);

    emailController = DelayedTextEditingController(
        notifyListeners,
        (s) => profileRepo.updateEmailAddress(s),
        (s) async => s.isNotEmpty ? null : 'Ouch email is required',
        emailAddress);
  }

  late final DelayedTextEditingController emailController;
  late final DelayedTextEditingController nameController;

  final ProfileRepo profileRepo;
}

class MainApp extends StatefulWidget {
  const MainApp({super.key});

  @override
  State<MainApp> createState() => _MainAppState();
}

class _MainAppState extends State<MainApp> {
  Controller controller =
      Controller(ProfileRepo(), 'Bob Smith', '[email protected]');

  @override
  Widget build(BuildContext context) => MaterialApp(
        home: Scaffold(
          body: AnimatedBuilder(
            animation: controller,
            builder: (context, child) => Center(
              child: Padding(
                padding: const EdgeInsets.all(50),
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: [
                    TextField(
                      controller: controller.nameController.textController,
                      decoration: InputDecoration(
                          errorText: controller.nameController.errorMessage),
                    ),
                    TextField(
                      controller: controller.emailController.textController,
                      decoration: InputDecoration(
                          errorText: controller.emailController.errorMessage),
                    )
                  ],
                ),
              ),
            ),
          ),
        ),
      );
}