Inheritance

Inheritance is an integral part of object-oriented programming (OOP). It allows a class to derive properties and characteristics from another class.

Example

The following example demonstrates the usage of inheritance in Dart:

class Animal {
  String name;

  Animal(this.name);

  void makeSound() {
    print('$name makes a sound.');
  }
}

class Dog extends Animal {
  Dog(String name) : super(name);

  @override
  void makeSound() {
    print('$name barks.');
  }

  void fetch() {
    print('$name is fetching!');
  }
}

void main() {
  Dog dog = Dog('Buddy');
  dog.makeSound();
  dog.fetch();
}

The output would be:

Buddy barks.
Buddy is fetching!

Types of Inheritance

There are different types of inheritance that can be implemented in Dart. These types are discussed one-by-one below.

Single Inheritance

Single inheritance is when a class inherits from a base (or super) class. This is the most common form of inheritance:

class Animal {
  void eat() {
    print('Animal is eating');
  }
}

class Dog extends Animal {
  void bark() {
    print('Dog is barking');
  }
}

void main() {
  Dog dog = Dog();
  dog.eat();
  dog.bark();
}

The output would be the following:

Animal is eating
Dog is barking

Multilevel Inheritance

Multilevel inheritance is when a class inherits from another derived class, forming a chain of inheritance:

class Animal {
  void eat() {
    print('Animal is eating');
  }
}

class Mammal extends Animal {
  void walk() {
    print('Mammal is walking');
  }
}

class Dog extends Mammal {
  void bark() {
    print('Dog is barking');
  }
}

void main() {
  Dog dog = Dog();
  dog.eat();
  dog.walk();
  dog.bark();
}

The below would be the output:

Animal is eating
Mammal is walking
Dog is barking

Hierarchical Inheritance

Hierarchical inheritance occurs when multiple classes inherit from the same base class:

class Animal {
  void eat() {
    print('Animal is eating');
  }
}

class Dog extends Animal {
  void bark() {
    print('Dog is barking');
  }
}

class Cat extends Animal {
  void meow() {
    print('Cat is meowing');
  }
}

void main() {
  Dog dog = Dog();
  Cat cat = Cat();

  dog.eat();
  dog.bark();

  cat.eat();
  cat.meow();
}

Here is the output:

Animal is eating
Dog is barking
Animal is eating
Cat is meowing