Flutter / SQL / Singleton / Threads

SQL

In pubspec.yaml add

Add dependencies

dependencies:

flutter:

sdk: flutter

sqflite: any

path_provider: any

intl: ^0.15.7

^ Means above or equal to that version



SINGLETON

class DbHelper{

static final DbHelper _dbHelper = DbHelper._internal();

DbHelper._internal();

factory DbHelper(){

return _dbHelper;

}

}

Threads
Can be used with Futures or Sync & Wait

Initialize a DB

import 'package:sqflite/sqflite.dart';

import 'dart:async';

import 'dart:io';

import 'package:path_provider/path_provider.dart';

static Database _db;

Future<Database> get db async {

if (_db == null) {

_db = await initializeDb();

}

return _db;

}

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 version) async {

await db.execute(

"CREATE TABLE $tblTodo( $colId INTEGER PRIMARY KEY, $colTitle TEXT, $colDdescription TEXT, $colPriority INTEGER, $colDate TEXT )");

}

Funtional Methods

Future<int> insertTodo(Todo todo) async {

Database db = await this.db;

var result = await db.insert(tblTodo, todo.toMap());

return result;

}

Future<List> geTodo() async {

Database db = await this.db;

var result =

await db.rawQuery("SELECT * FROM $tblTodo 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 $tblTodo"));

return result;

}

Future<int> updateTodo(Todo todo) async {

Database db = await this.db;

var result = await db.update(tblTodo, todo.toMap(), where: "$colId = ?", whereArgs: [todo.id]);

return result;

}

Future<int> deleteTodo(int id) async {

Database db = await this.db;

int result = await db.rawDelete("delete from $tblTodo where $colId = $id");

return result;

}

Use of Db

DbHelper helper = DbHelper();

List <Todo> todos = List<Todo>();

helper.initializeDb().then(

(result) => helper.geTodo().then((result) => todos=result));

DateTime today = DateTime.now();

Todo todo = Todo("Buy Melon", 3, today.toString(), "make sure they are good");

helper.insertTodo(todo);

OR

final dbFuture = helper.initializeDb();

dbFuture.then((result) {

final todosFuture = helper.geTodo();

todosFuture.then((result) {

List<Todo> todoList = List<Todo>();

count = result.length;

for (var i = 0; i < count; i++) {

todoList.add(Todo.fromObject(result[i]));

debugPrint(todoList[i].title);

}

});

});