Null safety

lib/app.dart

@@ -6,7 +6,7 @@ import 'pages/home/home_bloc.dart';
 import 'pages/home/home_page.dart';
 
 class MyApp extends StatelessWidget {
-  const MyApp({Key key}) : super(key: key);
+  const MyApp({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

lib/data/contact_repository_impl.dart

@@ -1,3 +1,6 @@
+import 'package:built_collection/built_collection.dart';
+import 'package:collection/collection.dart';
+
 import '../domain/contact.dart';
 import '../domain/contact_repository.dart';
 import 'local/dao/contact_dao.dart';
@@ -9,39 +12,36 @@ class ContactRepositoryImpl implements ContactRepository {
   const ContactRepositoryImpl(this._contactDao);
 
   @override
-  Stream<List<Contact>> search({String query = ''}) {
-    return _contactDao.search(query).map((entities) {
-      return entities.map(_toContact).toList(growable: false);
-    });
+  Stream<BuiltList<Contact>> search({required String by}) {
+    return _contactDao.search(by).map(
+        (entities) => entities.map(_toContact).whereNotNull().toBuiltList());
   }
 
   @override
-  Stream<Contact> getContactById(int id) {
-    return _contactDao.findById(id).map(_toContact);
-  }
+  Stream<Contact?> getContactById(int id) =>
+      _contactDao.findById(id).map(_toContact);
 
   @override
-  Future<bool> delete(Contact contact) {
-    return _contactDao.deleteById(contact.id);
-  }
+  Future<bool> delete(Contact contact) => _contactDao
+      .deleteById(ArgumentError.checkNotNull(contact.id, 'Contact id'));
 
   @override
-  Future<bool> insert(Contact contact) {
-    return _contactDao.insert(_toEntity(contact));
-  }
+  Future<bool> insert(Contact contact) =>
+      _contactDao.insert(_toEntity(contact));
 
   @override
-  Future<bool> update(Contact contact) {
-    return _contactDao.update(_toEntity(contact));
-  }
+  Future<bool> update(Contact contact) =>
+      _contactDao.update(_toEntity(contact));
 
   @override
-  Future<void> deleteAll() {
-    return _contactDao.deleteAll();
-  }
+  Future<void> deleteAll() => _contactDao.deleteAll();
 }
 
-Contact _toContact(ContactEntity entity) {
+Contact? _toContact(ContactEntity? entity) {
+  if (entity == null) {
+    return null;
+  }
+
   return Contact(
     (b) => b
       ..id = entity.id

lib/data/local/dao/contact_dao.dart

@@ -3,7 +3,7 @@ import 'contact_entity.dart';
 abstract class ContactDao {
   Stream<List<ContactEntity>> search(String query);
 
-  Stream<ContactEntity> findById(int id);
+  Stream<ContactEntity?> findById(int id);
 
   Future<bool> deleteById(int id);
 

lib/data/local/dao/contact_dao_impl.dart

@@ -31,7 +31,7 @@ class ContactDaoImpl implements ContactDao {
   }
 
   @override
-  Stream<ContactEntity> findById(int id) {
+  Stream<ContactEntity?> findById(int id) {
     return Stream.fromFuture(_briteDatabaseFuture).flatMap((db) {
       return db
           .createQuery(

lib/data/local/dao/contact_entity.dart

@@ -1,24 +1,23 @@
-import 'package:meta/meta.dart';
 
 import 'contact_entry.dart';
 
 class ContactEntity {
-  final int id;
+  final int? id;
   final String name;
   final String phone;
   final String address;
   final bool male;
   final DateTime updatedAt;
-  final DateTime createdAt;
+  final DateTime? createdAt;
 
   const ContactEntity({
-    @required this.id,
-    @required this.name,
-    @required this.phone,
-    @required this.address,
-    @required this.male,
-    @required this.updatedAt,
-    @required this.createdAt,
+    required this.id,
+    required this.name,
+    required this.phone,
+    required this.address,
+    required this.male,
+    required this.updatedAt,
+    required this.createdAt,
   });
 
   factory ContactEntity.fromJson(Map<String, dynamic> json) {

lib/domain/contact.dart

@@ -4,8 +4,7 @@ import 'package:built_value/built_value.dart';
 part 'contact.g.dart';
 
 abstract class Contact implements Built<Contact, ContactBuilder> {
-  @nullable
-  int get id;
+  int? get id;
 
   String get name;
 
@@ -17,8 +16,7 @@ abstract class Contact implements Built<Contact, ContactBuilder> {
 
   DateTime get updatedAt;
 
-  @nullable
-  DateTime get createdAt;
+  DateTime? get createdAt;
 
   Contact._();
 

lib/domain/contact_repository.dart

@@ -1,9 +1,11 @@
+import 'package:built_collection/built_collection.dart';
+
 import 'contact.dart';
 
 abstract class ContactRepository {
-  Stream<List<Contact>> search({String query = ''});
+  Stream<BuiltList<Contact>> search({required String by});
 
-  Stream<Contact> getContactById(int id);
+  Stream<Contact?> getContactById(int id);
 
   Future<bool> delete(Contact contact);
 

lib/pages/detail/detail_bloc.dart

@@ -7,22 +7,18 @@ import '../../domain/contact.dart';
 import '../../domain/contact_repository.dart';
 
 class DetailBloc extends DisposeCallbackBaseBloc {
-  final DistinctValueStream<Contact> contact$;
+  final DistinctValueStream<Contact?> contact$;
 
-  DetailBloc._(
-    this.contact$,
-    Func0<void> dispose,
-  ) : super(dispose);
+  DetailBloc._(this.contact$, VoidAction dispose) : super(dispose);
 
   factory DetailBloc(
     final ContactRepository contactRepo,
     final Contact initial,
   ) {
-    assert(contactRepo != null, 'contactRepo cannot be null');
-    assert(initial != null, 'initial cannot be null');
+    final id = ArgumentError.checkNotNull(initial.id, 'Contact id');
 
     final contact$ =
-        contactRepo.getContactById(initial.id).publishValueDistinct(initial);
+        contactRepo.getContactById(id).publishValueDistinct(initial);
 
     final bag = DisposeBag([
       contact$.debug(identifier: '[DETAIL_BLOC] contact').collect(),

lib/pages/detail/detail_page.dart

@@ -10,7 +10,7 @@ import '../edit_or_add/edit_or_add_page.dart';
 import 'detail_bloc.dart';
 
 class DetailPage extends StatefulWidget {
-  const DetailPage({Key key}) : super(key: key);
+  const DetailPage({Key? key}) : super(key: key);
 
   @override
   _DetailPageState createState() => _DetailPageState();
@@ -19,8 +19,8 @@ class DetailPage extends StatefulWidget {
 class _DetailPageState extends State<DetailPage> {
   final _dateFormat = DateFormat.yMd().add_Hms();
   final scrollController = ScrollController();
-  double _scale;
-  double _top;
+  var _scale = 0.0;
+  var _top = 0.0;
 
   void calculateScaleAndTop() {
     final defaultTopMargin = 256.0 - 23.0;
@@ -66,7 +66,7 @@ class _DetailPageState extends State<DetailPage> {
     final height = MediaQuery.of(context).size.height;
 
     return Scaffold(
-      body: RxStreamBuilder<Contact>(
+      body: RxStreamBuilder<Contact?>(
         stream: bloc.contact$,
         builder: (context, contact) {
           return Stack(
@@ -180,7 +180,7 @@ class _DetailPageState extends State<DetailPage> {
             leading: Icon(Icons.create),
             title: Text('Created at: '),
             subtitle: Text(
-              _dateFormat.format(contact.createdAt),
+              _dateFormat.format(contact.createdAt!),
             ),
           ),
           ListTile(