Inheritance

A feature that allows the derivation of a new class from an existing class. Introduces a way to reuse existing code without duplicating them.

A subclass inherits all the functionality of a superclass, but can also have its own unique attributes and methods.

Terminologies

Term	Definition
Superclass (also parent or base class)	The class from which subclasses can be created from
Subclass (also child or derived class)	The class that inherits a superclass

Declaration

In many OOP-based languages, a subclass can be created using the : symbol as such:

• C#

// CashCard is an existing class that is the superclass.
// MemberCashCard is the new class deriving from CashCard.
class MemberCashCard: CashCard
{
	// Unique attributes, properties, and methods
}

• Python

# CashCard is an existing class that is the superclass.
# MemberCashCard is the new class deriving from CashCard.
class MemberCashCard(CashCard):
	# Unique attributes, properties, and methods

Inheriting superclass

A subclass can call upon the superclasses’s attributes and properties, though the exact method differs across programming languages.

Some examples when inheriting superclass is used include:

• calling the superclass’s constructors to initialise the attributes in the superclass;

• calling the superclass’s printing method to retrieve information in the superclass; and

• calling a method in the superclass.

• C#

// Defining the constructor for MySubClass
public MySubClass(subparams) : base(superparams)
{
	// other initialization
}