Object Oriented Programming Principles

1. Lecturer: Kalamullah Ramli Electrical Engineering Dept. University of Indonesia Session-3 Object Oriented Programming Principles

2. Object-Oriented Programming:A New Programming Paradigm… • What is Matlab's programming paradigm? • Matlab is procedural: the focus is on the functions (procedures) • What is the programming paradigm in OOP? • As the name suggests, in OOP the focus is on • OBJECTS • This doesn't say much unless we understand what we mean with the term Object… So let's move on.

3. Objects Combine Properties & Behavior [1/2] • Remember following Structures: • person.firstname = 'John'; • person.lastname = 'Leonard'; • person.address1 = '803 Shallowford Lane'; • person.city = 'Peachtree City'; • person.state = 'GA'; • person.zip = '30269-4289'; • A structure contains data in an organized fashion.

4. Objects Combine Properties & Behavior [2/2] • If we add functions or methods to a structure, it becomes an object: • person.print_address(); • person.set_lastName('Paredis');

5. More Examples of Objects [1/2] • Car: • Properties: color, speed, fuel consumption, HP… • Behaviors: start, stop, turning, … • Triangle: • Properties: area, perimeter, linestyle, location,… • Behaviors: translate, rotate, shrink, flip,… • Date: • Properties: year, month, day, … • Behaviors: setDate, getMonth, isGreater, …

6. More Examples of Objects [1/2] • Properties: information about the object • Behaviors: methods to set, get and process properties • Combining properties and behaviors in objects is called • Encapsulation

7. Messages Code Data Objects Combine Properties and Behavior:So What? Why should we care? [1/2] • Black Box Philosophy: • Objects perform computation by making requests of each other through the passing of messages • The only way to interact with an object is through its methods! http://java.sun.com/docs/books/tutorial/java/concepts/object.html http://catalog.com/softinfo/objects.html

8. Objects Combine Properties and Behavior:So What? Why should we care? [2/2] • This is called Information Hiding • (the data is hidden from the user) • The collection of all methods is called the interface of the object http://java.sun.com/docs/books/tutorial/java/concepts/object.html http://catalog.com/softinfo/objects.html

9. Encapsulation and Data Hiding [1/2] • Properties (Variables) • Speed • RPM • Current Gear • Methods (Functions) • Braking • Acceleration • Turn • Changing Gears

10. Encapsulation and Data Hiding [2/2] • These methods are independent of how the bicycle has been built (hides the implementation) • You can control access to members of an object

11. Working with Objects: Messages [1/2] • Objects perform computation by making requests of each other through the passing of messages • Parts of a message – • The object to which the message is addressed • The name of the method to perform • Any parameters needed by the method\

12. Working with Objects: Messages [2/2] • Different objects may respond differently to an identical message: • bicycle.changeGears(lowerGear) • car.changeGears(lowerGear) • The same name and the same argument, but a different method = POLYMORPHISM • A method is defined only in the scope of a particular type of object, called class • Polymorphism is also called: function overloading

13. Class and Object [1/2] • Now that we know what an object is all about, let's look at how we can organize these objects • Class = A blueprint, or prototype, that defines the variables and the methods common to all objects of a certain kind Objects are individual instances of a class

14. House Plans: the architectural drawings that describe how a house is to be constructed A House: The house built from the plans is an instance of the House Class. The process of building the house is called Instantiation Class and Object [2/2]

15. Super class(parent) Sub class(child) Organizing Objects: Inheritance [1/2] • Children inherit • properties • behaviors

16. Organizing Objects: Inheritance [2/2] • Sub class (Child) • A class that is derived from a particular class, perhaps with one or more classes in between • Super class (Parent) • A class from which a particular class is derived, perhaps with one or more classes in between • Inheritance promotes • Reuse of code • Better Management of code

17. Abstraction in OOP [1/2] • Abstractions reveal causes and effects, expose patterns and frameworks and separate what's important from what's not • Abstraction in programming helps you make your ideas concrete in your code without obscuring the architecture with details • In procedural languages: • structures and functions are abstractions

18. Abstraction in OOP [2/2] OOP takes abstraction one step further through: • encapsulation • data hiding • polymorphism • Inheritance

19. Object-Oriented Programming [1/2] • A Quick Review: • “OOP is more a way of thinking than just a programming technique” – “conceptual tool that you use in thinking how to solve a problem” • Computer objects form the basis • Objects treated as real life objects • Identities • Properties • Behaviors • Data and functionality encapsulated in an object • Data hidden behind methods Abstraction

20. Object-Oriented Programming [2/2] • Objects organized in class hierarchies: inheritance • Objects interact through messages – methods • Polymorphism: the same message has a different meaning for different objects

21. Benefits of Object Oriented Programming • Analysis and Design made easier • Understanding of code made easier • Code Reuse • Ease of maintenance and enhancement • Simplifies collaboration • Fewer and shorter design iterations Abstraction

22. Examples of Programming Languages • Procedural languages • C • FORTRAN • BASIC • Pascal • Object Oriented languages • C++ • Smalltalk • Java

23. Object-Oriented Procedural Assignment#2a: OOP vs Procedural Programming Due date: Friday, February 27th, 2004

24. Assignment#2b: Object Oriented Philosophy • “Simulate the functionality of your computer using the object oriented philosophy” • Draw a diagram of the components present in the computer. What is the flow of information between these components? Leverage from previous lectures. • Identify the classes and objects that you would need to simulate these components. How do these classes interact? • Identify the variables and methods that you would assign to each class. Due Date: Friday, March 5th, 2004

25. References and Additional Reading • “Object Oriented Programming, ” http://www.toodarkpark.net/computers/objc/oop.html • “Core Java, ” Cay S. Horstmann and Gary Cornell, Sun Microsystems • “Thinking in C++, ” Bruce Eckel, http://www.mindview.net/Books/TICPP/ThinkingInCPP2e.html • “ Introduction to Object Oriented Programming, ” Timothy Budd, ftp://ftp.cs.orst.edu/pub/budd/oopintro/3rdEdition/info.html

26. Closure • Learning • Object oriented programming is more a philosophy than mere technique to develop programs… • This philosophy provides modularity to programs • Modularity provides openness to change… • Enables developing complex systems • Food for Thought • How will object oriented philosophy help in the future of software development? • How can the object oriented philosophy based on modularity be used in your field of specialization? • What changes are required to adapt this philosophy to your field?

27. The End QUESTIONS & COMMENTS ?