object oriented programming: classes and objects

Object Oriented Programming: Classes and Objects

Classes and Objects 2

What is OOP?

A programming technique first introduced in the 1960s but did not enter mainstream programming until 30 years later

Why was it developed? As computers became mainstream tools in business and

science, more and more real-world applications were developed

These were more complex than earlier applications and thus the programming was more complex as well (weather prediction, space exploration, war game simulation to name a few)

Procedural programming did not easily lend itself to designing complex systems

Object-oriented programming was deployed in part as an attempt to address this problem

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Procedural Programming Bank has hundreds of thousands of customers

Each customer has lots of information describing itself Name Address Id number Phone number Cell phone number E-mail address History off activities (at least a year’s worth)

Deposits Withdrawals Transfers Bill payments

etc, etc

How have we stored information of this type until now? How do we define what actions we can do for a customer?

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Procedural Programming The information about each individual customer is not in

one place An array holds one piece of information in a particular

location for a customer and all other arrays hold their information in the same index

For example, subscript 123 is the location in each array for a particular customer

id[123] 87634WD9 name[123] Fran Best address[123] 657 8th Ave city[123]New Haven state[123]CT zip[123]06071 phone[123] 203-765-0128 cell[123]203-879-0932

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Limitations of Procedural Programming

If the data structures change, many functions must also be changedData and functions are separate entities

As programs become larger and more complex, the separation of a program’s data and the code that operates on the data can lead to problemsdifficult to understand and maintaindifficult to modify and extendeasy to break

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Limitations of Procedural Programming

Procedural programming works, but it doesn’t fit what happens in the real world

Think of a customer’s information as being stored in a folder in a file cabinet.

To find out anything about the customer, you should be able to open the customer’s folder and examine all the paperwork.

Object oriented programming provides a more “natural” way to simulate the real-world via classes and objects

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Object Oriented Programming What is a class?

A class is a blueprint of something real. A class describes what type of characteristics or properties

something real can have but it itself is not real

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Object oriented Programming

The blueprint of a house tells you the dimensions of the house and locations of the rooms

When building the house, the specific materials to use, paint colors, wall paper, floors, etc. are subject to individual taste. This makes each home different from one another.

Each home is an actual implementation or instance of the blueprint – each specific house is an object of the house class

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Object Oriented ProgrammingOOP programming is centered on creating

objects from classes

An object is a software entity that contains both data and procedures

It is a self-contained unit consisting of attributes (data) and procedures (methods or functions)

The data is known as the object’s attributes

The procedures that an object performs are called member methods or functions

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Class and Object Example

Bank Account

Frank’s account

Janet’s account

Richard’s account

What do these three accounts

have in common?

Where do they differ?

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Introduction to ClassesObjects are created from a class

A class has no memory allocated to it (since it’s not real) while an object does

The first letter of the class is capitalized to show it is not a variable name

Format:class ClassName{

declaration;declaration;

};

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Introduction to Classes

By declaring a class, you are actually creating a new data type that you can use as you would int, double, bool, etc.

The class name is used to declare objects of the class

The class name can also be used to describe a parameter being passed to a function

Declaring a Class

class BankAccount

{

public:

int id;

string name;

double balance;

};

Declaring Objects of the Classint main(){ BankAccount Frank, Janet, Richard;

Frank.id = 1234; Frank.name= "Frank Smith"; Frank.balance = 789.23;

Janet.id = 6098; Janet.name= "Janet Brooks"; Janet.balance = 3028.56;

Richard.id = 4387; Richard.name = "Richard Forest"; Richard.balance = 100.00;

cout<<Janet.id<<" "<<Janet.name<< <<" "<< Janet.balance<<endl;

return 0;}

Exercise

Write a function printBankAccount that accepts an object of the class BankAccount as a parameter and prints the id, name and balance of the account. No value is returned.

Using Objects

We can make an arrays of objects of a class and use them to store information about accounts

This gives us the ability to use a loop control to go one by one through the accounts and process them as needed

Exercise

Write a function printAllBankAccounts that accepts an array of objects of the class BankAccount as a parameter and prints the id, name and balance of all the account. No value is returned.

Starting Code#include <iostream>using namespace std;class BankAccount{ public: int id; string name; double balance; };

void printBankAccount(BankAccount);void printAllBankAccounts(BankAccount[]);

int main(){ BankAccount ba[3]; ba[0].id = 1234; ba[0].name= "Frank Smith"; ba[0].balance = 789.23; ba[1].id = 6098; ba[1].name= "Janet Brooks"; ba[1].balance = 3028.56; ba[2].id = 4387; ba[2].name = "Richard Forest"; ba[2].balance = 100.00;

printBankAccount(ba[0]); cout<<endl<<endl; return 0;}

void printBankAccount(BankAccount ba){//FILL IN CODE HEREreturn;}