Dart - Concept of Inheritance - GeeksforGeeks

20 Jul, 2020
In Dart, one class can inherit another class i.e dart can create a new class from an existing class. We make use of extend keyword to do so.
Terminology:  
Parent Class: It is the class whose properties are inherited by the child class. It is also known as a base class or superclass.
Child Class: It is the class that inherits the properties of the other classes. It is also known as a deprived class or subclass.
class parent_class{
...
}

class child_class extends parent_class{
...
}

Example 1: Example of Single Inheritance in the dart. 
Dart
// Dart program to show the single inheritance  // Creating parent classclass Gfg{      // Creating a function  void output(){    print("Welcome to gfg!!\nYou are inside output function.");  }}  // Creating Child classclass GfgChild extends Gfg{  // We are not defining  // any thing inside it...}void main() {  // Creating object of GfgChild class  var geek = new GfgChild();      // Calling function  // inside Gfg(Parent class)  geek.output();}
 
Output: 
Welcome to gfg!!
You are inside output function.

Types of Inheritance: 
Single Inheritance: When a class inherits a single parent class than this inheritance occurs.Multiple Inheritance: When a class inherits more than one parent class than this inheritance occurs. Dart doesn’t support this.Multi-Level Inheritance: When a class inherits another child class than this inheritance occurs. Hierarchical Inheritance: More than one classes have the same parent class.
Single Inheritance: When a class inherits a single parent class than this inheritance occurs.
Multiple Inheritance: When a class inherits more than one parent class than this inheritance occurs. Dart doesn’t support this.
Multi-Level Inheritance: When a class inherits another child class than this inheritance occurs.
 Hierarchical Inheritance: More than one classes have the same parent class.
Important Points: 
Child classes inherit all properties and methods except constructors of the parent class.Unlike Java, Dart also doesn’t support multiple inheritance.
Child classes inherit all properties and methods except constructors of the parent class.
Unlike Java, Dart also doesn’t support multiple inheritance.
Example 2:
Dart
// Dart program for multilevel interitance  // Creating parent classclass Gfg{      // Creating a function  void output1(){    print("Welcome to gfg!!\nYou are inside the output function of Gfg class.");  }}  // Creating Child1 classclass GfgChild1 extends Gfg{      // Creating a function  void output2(){    print("Welcome to gfg!!\nYou are inside the output function of GfgChild1 class.");  }}  // Creating Child2 classclass GfgChild2 extends GfgChild1{  // We are not defining  // any thing inside it...}  void main() {  // Creating object  // of GfgChild class  var geek = new GfgChild2();      // Calling function  // inside Gfg  //(Parent class of Parent class)  geek.output1();      // Calling function  // inside GfgChild  // (Parent class)  geek.output2();}
 
Output:  
Welcome to gfg!!
You are inside the output function of Gfg class.
Welcome to gfg!!
You are inside the output function of GfgChild1 class.

Example 3: Hierarchical inheritance.  
Dart
// Dart program for Hierarchical inheritance  // Creating parent classclass Gfg{      // Creating a function  void output1(){    print("Welcome to gfg!!\nYou are inside output function of Gfg class.");  }}  // Creating Child1 classclass GfgChild1 extends Gfg{  // We are not defining  // any thing inside it...}  // Creating Child2 classclass GfgChild2 extends Gfg{      // We are not defining  // any thing inside it...}  void main() {  // Creating object  // of GfgChild1 class  var geek1 = new GfgChild1();      // Calling function  // inside Gfg(Parent class)  geek1.output1();      // Creating object of  // GfgChild1 class  var geek2 = new GfgChild2();      // Calling function  // inside Gfg(Parent class)  geek2.output1();}
 
Output: 
Welcome to gfg!!
You are inside output function of Gfg class.
Welcome to gfg!!
You are inside output function of Gfg class.

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Dart
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