07 iec t1_s1_oo_ps_session_10

Object-Oriented Programming Using C#
Objectives

In this session, you will learn to:
Implement operator overloading
Identify relationships between classes
Use classes and inheritance

Ver. 1.0 Session 10 Slide 1 of 21

Overloading Unary Operators

Unary operators act on a single operand. Some examples
of unary operators are the increment (++) and decrement
(--) operators.
Unary operators can be classified as:
Simple prefix unary operators, for example the – (minus)
operator.
Pre and post increment and decrement operators, for example
the ++() prefix increment operator.
The implementation of the increment operator used with
structs cannot be implemented with classes.


Overloading Binary Operators

Binary operators are operators that work with two operands.
Binary operators include the arithmetic operators (+, -, *, /,
%), arithmetic assignment operators (+=, -=, *=, /=. %=),
and comparison operators (<, >, <=, >=, ==, !=).
Overloading a binary operator is similar to overloading a
unary operator, except that a binary operator requires an
additional parameter.
Following is the syntax of binary overloading in C#:
operator <operator>(Object1,Object2);


Demo: Overloading an Operator

Problem Statement:
FunCity Land is a newly established amusement park located
in West Virginia. Brad is a chief technical officer of FunCity
Land. He is currently working on a project related with
calculating distances. This project will calculate the distance to
reach FunCity Land from various locations because many
visitors do not know the exact location of the park.
Brad needs to develop a program, which would enter a visitor’s
location and the distance traveled by the visitor till that point.
After analyzing the location and the distance traveled by the
visitor, the program should display the remaining distance and
the total distance traveled.
Help Brad to develop an application by overloading the binary
operator(+).


Demo: Overloading an Operator (Contd.)

Solution:
To develop the required application, Brad needs to perform the
following tasks:
1. Create a console-based application.
2. Build and execute an application.


Identifying Relationships Between Classes

In software application, classes and objects are related to
each other.
In the object-oriented approach, objects perform actions in
response to messages from other objects defining the
recipient object’s behavior.
This approach specifies the relationships among classes
based on the behavior of individual class.


Kinds of Relationships

There are various relationships between objects of different
classes in an object-oriented environment:
Inheritance Relationship:
Object-oriented programming enables classes to inherit commonly
used state and behavior from other classes.
In C# programming, a class is allowed to inherit from another
class.
Generalization is needed to create programs that can be
customized in accordance with new requirements.
Let us understand the concept of inheritance relationship
with the help of an example.


Kinds of Relationships (Contd.)

Parent Class



Parent Class

Child Class



Parent Class

Child Class
Deriving the features of parents,
such as height, complexion, and
Behavior



You can also establish a relationship between a superclass
and its subclasses.
The following figure shows the hierarchy of the subclasses
of a superclass.
Automobile

Car Bus

Ford BMW Toyota Mitsubishi



• Composition Relationship:
Object-oriented programming allows you to form an object,
which includes another object as its part. This mechanism of
forming an object is called composition.
• Utilization Relationship:
Object-oriented programming allows a class to make use of
another class. This kind of relationship is called utilization.
• Instantiation Relationship:
Object-oriented programming allows a relationship between a
class and an instance of that class. This kind of relationship is
called instantiation.


Just a minute

Build the hierarchy of the mixer, VCR, color television,
washing machine, stereo class objects, and generalize
wherever possible.

Answer:
The figure shows the hierarchy of the class objects.

Electronic Items

Entertainment Items Utility Items

Color VCR Stereo Washing
Mixer
Television Machine


Just a minute

Identify the relationship between the following class pairs:
1. Television – Speaker
2. Mammal – Tiger
3. Garment – Shirt
4. Cup – Tea
5. Computer – Microprocessor

Answer:
5 and 1 are examples of composition relationships.
3 and 2 are examples of inheritance relationships.
4 does not exhibit any relationship. Tea is not an attribute of
cup.


Just a minute

Identify the classes and their utilization relationship in the
following scenario of a departmental store.
There are several counters and each counter in the store is
manned by a single salesperson who sells a specific
product. A customer approaches a counter. Depending on
the customer’s desire to purchase a product, the
salesperson sells the product to the customer and accepts
payment.

Answer:
The utilization relationship of the preceding scenario are:
Salespersons man the counters.
Each counter deals in a specific product.
The customer buys a product.
The customer pays the salesperson.


Using Classes and Inheritance

In C#, inheritance is the property by which the objects of a
derived class possess copies of the data members and the
member functions of the base class.
A class that inherits or derives attributes from another class
is called the derived class.
The class from which attributes are derived is called the
base class.
In object-oriented programming, the base class is actually a
superclass and the derived class is a subclass.


Implementing Inheritance

Each instance of the derived class includes the attributes of
the base class.
Any change made to the base class automatically changes
the behavior of its derived classes.
The syntax used in C# for creating derived classes is as
follows:
<access-specifier> class <base_class>
{
...
}
class <derived_class> : <base_class>
{
...
}


Implementing Inheritance (Contd.)

You can use the following thumb rule to establish whether
inheritance is required while you are designing a program.
Always check the kind of relationship between the derived
and the base class.
Ensure that the derived class can base class.
You can also use inherited classes with constructors.
In inheritance, the derived class receives the base class
member variables and methods. This means that an order of
inheritance must be followed during the construction of an
object.


Summary

In this session, you learned that:
Operators may be classified as unary and binary operators.
Unary operators work with one operand and are classified as:
• Simple prefix unary operators
• Pre and post increment and decrement operators
– A prefix unary operator may be defined by a member function
that takes no parameters or by a nonmember function that
takes one parameter.
– Binary operators work with two operands.
– Overloading a binary operator is similar to overloading a unary
operator, except that a binary operator requires an additional
parameter.


Summary (Contd.)

The four kinds of relationships that exist among classes are:
• Inheritance relationship
• Composition relationship
• Utilization relationship
• Instantiation relationship
– Object-oriented programming enables classes to inherit
commonly used state and behavior from other classes.
– Generalization means that multiple classes can inherit from the
same superclass.
– The composition relationship exists when one class is made up
of another class.
– The utilization relationship exists between two or more
unrelated classes if one class uses the other.


Summary (Contd.)

An instantiation relationship is a relationship between a class
and an instance of that class.
A class that inherits or derives attributes from another class is
called the derived class and the class from which it is derived
is called the base class.
Inheritance avoids redundancy in code and enables easy
maintenance of code.
Constructors are called in the order of base-to-derived.


07 iec t1_s1_oo_ps_session_10

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