Understanding Inheritance and Different Types of Inheritance

Inheritance is a mechanism of acquiring the features and behaviours of a class by another class. The class whose members are inherited is called the base class, and the class that inherits those members is called the derived class. Inheritance implements the IS-A relationship.

For example, mammal IS-A animal, dog IS-A mammal; Hence dog IS-A animal as well.

Different Types of Inheritance

OOPs support the six different types of inheritance as given below :

1. Single inheritance

2. Multi-level inheritance

3. Multiple inheritance

4. Multipath inheritance

5. Hierarchical Inheritance

6. Hybrid Inheritance

1. Single inheritance

   In this inheritance, a derived class is created from a single base class.

   In the given example, Class A is the parent class and Class B is the child class since Class B inherits the features and behavior of the parent class A.

   

   Syntax for Single Inheritance

   //Base Class
   class A 
   {
    public void fooA()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class B : A
   {
    public void fooB()
    {
    //TO DO:
    }
   }
   

2. Multi-level inheritance

   In this inheritance, a derived class is created from another derived class.

   In the given example, class c inherits the properties and behavior of class B and class B inherits the properties and behavior of class B. So, here A is the parent class of B and class B is the parent class of C. So, here class C implicitly inherits the properties and behavior of class A along with Class B i.e there is a multilevel of inheritance.

   

   Syntax for Multi-level Inheritance

   //Base Class
   class A 
   {
    public void fooA()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class B : A
   {
    public void fooB()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class C : B
   {
    public void fooC()
    {
    //TO DO:
    }
   }
   

3. Multiple inheritance

   In this inheritance, a derived class is created from more than one base class. This inheritance is not supported by .NET Languages like C#, F# etc. and Java Language.

   In the given example, class c inherits the properties and behavior of class B and class A at same level. So, here A and Class B both are the parent classes for Class C.

   

   Syntax for Multiple Inheritance

   //Base Class
   class A 
   {
    public void fooA()
    {
    //TO DO:
    }
   }
   
   //Base Class
   class B
   {
    public void fooB()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class C : A, B
   {
    public void fooC()
    {
    //TO DO:
    }
   }
   

4. Multipath inheritance

   In this inheritance, a derived class is created from another derived classes and the same base class of another derived classes. This inheritance is not supported by .NET Languages like C#, F# etc.

   In the given example, class D inherits the properties and behavior of class C and class B as well as Class A. Both class C and class B inherits the Class A. So, Class A is the parent for Class B and Class C as well as Class D. So it's making it Multipath inheritance.

   

   Syntax for Multipath Inheritance

   //Base Class
   class A
   {
    public void fooA()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class B : A
   {
    public void fooB()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class C : A
   {
    public void fooC()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class D : B, A, C
   {
    public void fooD()
    {
    //TO DO:
    }
   }
   

5. Hierarchical Inheritance

   In this inheritance, more than one derived classes are created from a single base class and futher child classes act as parent classes for more than one child classes.

   In the given example, class A has two childs class B and class D. Further, class B and class C both are having two childs - class D and E; class F and G respectively.

   

   Syntax for Hierarchical Inheritance

   //Base Class
   class A
   {
    public void fooA()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class B : A
   {
    public void fooB()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class C : A
   {
    public void fooC()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class D : C
   {
    public void fooD()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class E : C
   {
    public void fooE()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class F : B
   {
    public void fooF()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class G :B
   {
    public void fooG()
    {
    //TO DO:
    }
   }
   

6. Hybrid inheritance

   This is combination of more than one inheritance. Hence, it may be a combination of Multilevel and Multiple inheritance or Hierarchical and Multilevel inheritance or Hierarchical and Multipath inheritance or Hierarchical, Multilevel and Multiple inheritance.

   Since .NET Languages like C#, F# etc. does not support multiple and multipath inheritance. Hence hybrid inheritance with a combination of multiple or multipath inheritance is not supported by .NET Languages.

   

   Syntax for Hybrid Inheritance

   //Base Class
   class A
   {
    public void fooA()
    {
    //TO DO:
    }
   }
   
   //Base Class
   class F
   {
    public void fooF()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class B : A, F
   {
    public void fooB()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class C : A
   {
    public void fooC()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class D : C
   {
    public void fooD()
    {
    //TO DO:
    }
   }
   
   //Derived Class
   class E : C
   {
    public void fooE()
    {
    //TO DO:
    }
   }
   

Advantages of Inheritance

1. Reduce code redundancy.

2. Provides code reusability.

3. Reduces source code size and improves code readability.

4. Code is easy to manage and divided into parent and child classes.

5. Supports code extensibility by overriding the base class functionality within child classes.

Disadvantages of Inheritance

1. In Inheritance base class and child class, both are tightly coupled. Hence If you change the code of parent class, it will affect all the child classes.

2. In class hierarchy, many data members remain unused and the memory allocated to them is not utilized. Hence it effect performance of your program, if you have not implemented inheritance correctly.

What do you think?

In this article, you learned about the different types of inheritance including advantages and disadvantages. I would like to have feedback from my blog readers. Your valuable feedback, question, or comments about this article are always welcome.