Programming in Dart: Classes

Jun 28 2022 · Dart 2.17, Flutter 3.0, DartPad

Part 2: Learn Inheritance

15. Use Abstract Classes

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Previous episode: 14. Challenge: Override a Method Next episode: 16. Implement an Interface

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So far, things have been straightforward but with this episode, things are about to get a little abstract. I’m going to introduce you to abstract classes. But before we discuss abstract classes you need to understand the concept of an interface.

ImageGenerator generator = NetworkGenerator();
abstract class HelloWorld {

var hello = HelloWorld();
var message = 'Hello World!';
String getHelloString();
class BackwardsHello extends HelloWorld {

String getHelloString() {
    return message.split('').reversed.join();
class ShoutyHello extends HelloWorld {
  String getHelloString() {
    return message.toUpperCase();
HelloWorld hello = BackwardsHello();
hello = ShoutyHello();