Lesson 30 of 59

5 mins read

Inheritance, Method Overriding (@override) & super

In Plain English

Dart supports single class inheritance using the `extends` keyword. A subclass inherits all fields and methods from its superclass. Subclasses can override parent methods using the `@override` metadata annotation and call parent implementations using the `super` keyword (`super.method()`, `super(args)`).

The Mental Model

"Inheritance is like genetic traits passed from parent to child: a child inherits eye color and height potential from parents, but can develop their own unique skills (overridden methods)."

Deep Dive: How It Works

Single Inheritance: A class can extend only ONE superclass (mixins provide multi-source composition).

`@override` Annotation: Informs the compiler that a method is intended to override a parent method, catching typos at build-time.

`super` Constructor Forwarding: Subclasses delegate constructor initialization to the superclass with `: super(args)` or super initializing formals `Subclass(super.param)`.

Syntax Blueprint

class Animal {
  void makeSound() => print("Generic sound");
}

class Dog extends Animal {
  @override
  void makeSound() => print("Bark!");
}

Class extension and method overriding.

Core Rules to Remember

Single Inheritance (extends): Inherits properties and behaviors from a single direct parent class.

@override Safety: Guarantees the method signature matches a parent method.

super Initializing Formals: Dart 2.17+ supports `Subclass(super.id)` directly forward parameters.

Common Beginner Traps & How to Fix Them

Mistake:Forgetting to call `super.initState()` or `super.dispose()` in Flutter stateful widgets.

Why it happens: Omitting super calls prevents the framework from cleaning up internal listeners.

How to fix: Always include required super calls at the top/bottom of framework lifecycle methods.

Pro Tip: Use super initializing formals (`Subclass({required super.id, required super.name});`) to eliminate repetitive `super(id: id, name: name)` boilerplate.

Live Interactive Example

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Class Inheritance and Method Overriding in Action

Python 3.12

Output Console

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How it works: Manager inherited base fields from Employee and overridden calculatePay() adding bonus.

Your Turn: Micro Challenge

No pressure! Edit the starter code below and test your solution with instant feedback.

Micro Exercise

Extend Vehicle Class

Create class `Vehicle { void drive() => print("Driving vehicle"); }`.
Create class `Car extends Vehicle` that overrides `drive()` to print `"Driving car"`.
In `main()`, instantiate `Car().drive();`.

Sandbox Output

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