1. Object Oriented Programming: Classes and Objects

2. Classes and Objects2 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

3. Classes and Objects3 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?

4. Classes and Objects4 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 8 th Ave city[123]  New Haven state[123]  CT zip[123]  06071 phone[123]  203-765-0128 cell[123]  203-879-0932

5. C++: Classes & Objects - 1 5 Limitations of Procedural Programming If the data structures change, many functions must also be changed Data 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 problems difficult to understand and maintain difficult to modify and extend easy to break

6. Classes and Objects6 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

7. Classes and Objects7 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

8. Classes and Objects8 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

9. C++: Classes & Objects - 1 9 Object Oriented Programming OOP 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

10. C++: Classes & Objects - 1 10 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?

11. C++: Classes & Objects - 1 11 Introduction to Classes Objects 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; };

12. C++: Classes & Objects - 1 12 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

13. Declaring a Class class BankAccount { public: int id; string name; double balance; };

14. Declaring Objects of the Class int 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; }

15. 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.

16. 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

17. 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.

18. Starting Code #include 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 HERE return; }