How to fix factory DbHelper class in flutter? - flutter

Question

I have an error on the flutter run. Probably, some problem is on
//podesavanje singltona 2/3
DbHelper()._internal();
//podesavanje singltona 3/3
factory DbHelper() {
return _dbHelper;
}
in dbhelper.dart file. Any idea how to solve that?
dbhelper.dart
import 'package:sqflite/sqflite.dart';
import 'dart:async';
import 'dart:io';
import 'package:path_provider/path_provider.dart';
import 'package:todo_app/model/todo.dart';
class DbHelper {
//podesavanje singltona 1/3
static final DbHelper _dbHelper = DbHelper()._internal();
//table name
String tblName = "todo";
//columns
String colId = "id";
String colTitle = "title";
String colDescription = "description";
String colPriority = "priority";
String colDate = "date";
//podesavanje singltona 2/3
DbHelper()._internal();
//podesavanje singltona 3/3
factory DbHelper() {
return _dbHelper;
}
static Database _db;
Future<Database> get db async {
if (_db == null) {
_db = await initializeDb();
}
return _db;
}
//za ovo koristimo 'dart:io';
Future<Database> initializeDb() async {
Directory dir = await getApplicationDocumentsDirectory();
String path = dir.path + "todos.db";
var dbTodos = await openDatabase(path, version: 1, onCreate: _createDb);
return dbTodos;
}
void _createDb(Database db, int newVersion) async {
await db.execute(
"CREATE TABLE $tblName($colId INTEGER PRIMARY KEY, $colTitle TEXT, $colDescription TEXT, $colPriority INTEGER, $colDate TEXT)"
);
}
Future<int> insertTodo(Todo todo) async{
Database db = await this.db;
var result = await db.insert(tblName, todo.toMap());
return result;
}
Future<List> getTodos() async {
Database db = await this.db;
var result = await db.rawQuery("SELECT * FROM $tblName order by $colPriority ASC");
return result;
}
Future<int> getCount() async {
Database db = await this.db;
var result = Sqflite.firstIntValue(
await db.rawQuery("SELECT COUNT(*) FROM $tblName")
);
return result;
}
Future<int> updateTodo(Todo todo) async{
Database db = await this.db;
var result = await db.update(tblName, todo.toMap(), where: "$colId = ?", whereArgs: [todo.id]);
return result;
}
Future<int> deleteTodo(int id) async{
Database db = await this.db;
var result = await db.rawDelete("DELETE FROM $tblName WHERE $colId = $id");
return result;
}
}
todo.dart
import 'package:flutter/scheduler.dart';
class Todo {
//_ se stavlja zato da budu privatni
int _id;
String _title;
String _description;
String _date;
int _priority;
//postavljanje konstruktora, ne moze isti vise puta, opcioni ide u []
Todo(this._title, this._priority, this._date, [this._description]);
Todo.withId(this._id, this._title, this._priority, this._date,
[this._description]);
//geteri
int get id => _id;
String get title => _title;
String get description => _description;
String get date => _date;
int get priority => _priority;
//seteri
set title(String newTitle) {
if (newTitle.length < 255) {
_title = newTitle;
}
}
set description(String newDescription) {
if (newDescription.length < 255) {
_description = newDescription;
}
}
set priority(int newPriority) {
if (newPriority > 0 && newPriority <= 3) {
_priority = newPriority;
}
}
set date(String newDate) {
_date = newDate;
}
Map<String, dynamic> toMap() {
var map = Map<String, dynamic>();
map["title"] = _title;
map["description"] = _description;
map["priority"] = _priority;
map["date"] = _date;
if (_id != null) {
map["id"] = _id;
}
return map;
}
Todo.fromObject(dynamic o) {
this._id = o["id"];
this._title = o["title"];
this._description = o["description"];
this._date = o["date"];
this._priority = o["priority"];
}
}
main.dart
import 'package:flutter/material.dart';
import 'package:todo_app/util/dbhelper.dart';
import 'package:todo_app/model/todo.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
List<Todo> todos = List<Todo>();
DbHelper helper = DbHelper();
helper
.initializeDb()
.then((result) => helper.getTodos().then((result) => todos = result));
DateTime today = DateTime.now();
Todo todo = Todo("naslov", 1, today.toString(), "opcioni diskripsn");
helper.insertTodo(todo);
}
}
flutter run
Launching lib/main.dart on iPhone 8 Plus in debug mode...
Running Xcode build...
Xcode build done. 10.4s
Failed to build iOS app
Error output from Xcode build:
↳
** BUILD FAILED **
Xcode's output:
↳
lib/util/dbhelper.dart:19:13: Error: Expected '{' before this.
DbHelper()._internal();
^
lib/util/dbhelper.dart:19:13: Error: Expected a class member, but got '.'.
DbHelper()._internal();
^
lib/util/dbhelper.dart:21:11: Error: 'DbHelper' is already declared in this scope.
factory DbHelper() {
^^^^^^^^
lib/util/dbhelper.dart:19:3: Context: Previous declaration of 'DbHelper'.
DbHelper()._internal();
^^^^^^^^
lib/util/dbhelper.dart:7:7: Error: The non-abstract class 'DbHelper' is missing implementations for these members:
- DbHelper._internal
Try to either
- provide an implementation,
- inherit an implementation from a superclass or mixin,
- mark the class as abstract, or
- provide a 'noSuchMethod' implementation.
class DbHelper {
^^^^^^^^
lib/util/dbhelper.dart:19:14: Context: 'DbHelper._internal' is defined here.
DbHelper()._internal();
^^^^^^^^^
lib/main.dart:14:23: Error: Can't use 'DbHelper' because it is declared more than once.
DbHelper helper = DbHelper();
^
lib/util/dbhelper.dart:9:37: Error: Can't use 'DbHelper' because it is declared more than once.
static final DbHelper _dbHelper = DbHelper()._internal();
^
Command PhaseScriptExecution failed with a nonzero exit code
note: Using new build systemnote: Planning buildnote: Constructing build description

Answer 1

This is what you are trying to do
class DbHelper {
//podesavanje singltona 1/3
static final DbHelper _dbHelper = DbHelper._internal();
//table name
String tblName = "todo";
//columns
String colId = "id";
String colTitle = "title";
String colDescription = "description";
String colPriority = "priority";
String colDate = "date";
//podesavanje singltona 2/3
DbHelper._internal();
//podesavanje singltona 3/3
factory DbHelper() {
return _dbHelper;
}
static Database _db;
Future<Database> get db async {
if (_db == null) {
_db = await initializeDb();
}
return _db;
}
//za ovo koristimo 'dart:io';
Future<Database> initializeDb() async {
Directory dir = await getApplicationDocumentsDirectory();
String path = dir.path + "todos.db";
var dbTodos = await openDatabase(path, version: 1, onCreate: _createDb);
return dbTodos;
}
void _createDb(Database db, int newVersion) async {
await db.execute(
"CREATE TABLE $tblName($colId INTEGER PRIMARY KEY, $colTitle TEXT, $colDescription TEXT, $colPriority INTEGER, $colDate TEXT)");
}
Future<int> insertTodo(Todo todo) async {
Database db = await this.db;
var result = await db.insert(tblName, todo.toMap());
return result;
}
Future<List> getTodos() async {
Database db = await this.db;
var result =
await db.rawQuery("SELECT * FROM $tblName order by $colPriority ASC");
return result;
}
Future<int> getCount() async {
Database db = await this.db;
var result = Sqflite.firstIntValue(
await db.rawQuery("SELECT COUNT(*) FROM $tblName"));
return result;
}
Future<int> updateTodo(Todo todo) async {
Database db = await this.db;
var result = await db.update(tblName, todo.toMap(),
where: "$colId = ?", whereArgs: [todo.id]);
return result;
}
Future<int> deleteTodo(int id) async {
Database db = await this.db;
var result = await db.rawDelete("DELETE FROM $tblName WHERE $colId = $id");
return result;
}
}

Answer 2

Remove () from DbHelper()._internal()
DbHelper()._internal(); => DbHelper._internal();