iapicca

class Singleton {
  
  int _counter;
  
  static final Singleton _instance = Singleton._internal();
  factory Singleton()=> _instance;
  Singleton._internal() {
    _counter = 0;
  }
  

iapicca

import 'dart:async';

class Singleton {
  static final _instance = Singleton._internal();
  factory Singleton() => _instance;
  Singleton._internal() {}
  
  Duration _delay = Duration();
  Timer _reset;
  void _timeout() => _delay = Duration();

iapicca

import 'dart:convert';

const String _object_key = 'object';
const String _subset_key = 'subset';
const String _json = '{"object": [{"subset":"hello"},{"subset":" "},{"subset":"world"}]}';

void main() => print(jsonDecode(_json)[_object_key].map((d)=> d[_subset_key] as String).join());

iapicca

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: MyHomePage(),),);

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

iapicca

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) => MaterialApp( home: MyHomePage(),);
}

class MyHomePage extends StatelessWidget {

iapicca

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {

  static const String _message = '🐣';

  @override
  Widget build(BuildContext context) => MaterialApp( 

iapicca

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: MyApp()));

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

iapicca

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

void main() {
  runApp(MaterialApp(home: MyHome()),);
}

class MyHome extends StatelessWidget {
  @override
  Widget build(BuildContext context) => Scaffold(

iapicca

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: MyApp()));

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) => Scaffold(
    body: CustomScrollView(
      slivers: <Widget>[

iapicca

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: MyApp()));

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) => Scaffold(
    body: Center(
      child:DropDownWidget(),),);
}