function_vs_class.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  void _incrementCounter() {
    setState(() {
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ClassWidget(),
            getWidget(),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
  
  Widget getWidget () => FunctionWidget();
}

class ClassWidget extends StatelessWidget {
  @override
  StatelessElement createElement() {
    print("Created element for ClassWidget");
    return super.createElement();
  }
  
  @override
  Widget build(BuildContext context) {
    print("Inside ClassWidget build method");
    return Text("Class Widget");
  }
}

class FunctionWidget extends StatelessWidget {
  
  @override
  StatelessElement createElement() {
    print("Created element for FunctionWidget");
    return super.createElement();
  }
  
  
  @override
  Widget build(BuildContext context) {
    print("Inside FunctionWidget build method");
    return Text("Function Widget");
  }
}