OOP Presentation.pptx
- 2. • OOP is mainly a program design philosophy. • OOP uses a different set of programming languages than old procedural programming languages (C, Pascal, etc..,) • Everything in OOP is grouped as self sustainable “objects”. • Hence, you gain re-usability by means of four main object- oriented programming concepts.
- 3. • In OOP programmers define not only the data type of data structure, but also the type of operations/methods(functions) that can be applied to the data structure. • In this way, the data structure becomes an object that includes both data and functions (methods) in one unit. In addition, programmers can create relationships between one object and another. • For example, Objects can inherit characteristics from other objects.
- 4. Key idea in object-oriented: The real world can be “accurately” described as a collection of objects that interact.
- 5. Basic Terminology: Object usually a person, place or thing ( a noun) Method an action performed by an object (a verb) Property or attribute Characteristics of certain object. Class a category of similar objects, does not hold any values of the object’s attributes/properties
- 6. Classes and Objects • A class is a prototype, idea, and blueprint for creating objects. • An object is an instance of a class • For example, in C++ we define classes, which in turn are used to create objects • A class has a constructor for creating objects • Class is composed of three things: its name, attributes/properties, and methods.
- 7. Class Objects: Instances of the class Class Properties: Belong to the class Instance Properties: Belong to the object Methods: Functions of class
- 8. Class: A class is a definition of objects with the same properties and the same methods class Bicycle { int speed = 0; int gear = 1; void changeGear (int newValue) { gear = newValue; } void speedUp (int increment) { speed = speed + increment; } void applyBreakes (int decrement) { speed = speed – decrement; }
- 9. Account Owner Balance Account Number Transaction Log Deposit Account Interest Rate Current Account Over Draft Limit Example:
- 10. Almost everything in the world can be represented as an Object • A flower, a tree, an animal • A student, a professor • A desk, a chair, a classroom, a building • A university, a city, a country • The world, the universe • A subject such as CS, IS, Math, History • An information system, financial, legal, etc…, What is an Object? An object is an instance of a class.
- 11. Informally, an object represents an entity, either physical, conceptual, or software. Physical entity truck Conceptual entity chemical process Software entity linked list
- 12. Formal definition of an “Object” An Object is a computational entity that: • Encapsulates some state • Is able to perform actions, or methods, on this state • Communicates with other objects via message passing
- 13. Classes & Objects “X” CAR Property Plate No : AD47483 Color : Blue Manufacturer : Mercedes Model : Classic Gear Type : Automatic Method Moves forward Moves backward Moves right Moves left Stops
- 14. Time Hour Minute void addMinutes( int m ) inTime Attributes: Hour = 8 Minute = 30 Methods: void addMinutes( int m ) Class inTime Attributes: Hour = 8 Minute = 30 Methods: void addMinutes( int m ) Objects
- 15. • Each copy of an object from a particular class is called an instance of the class • The act of creating a new instance of an class is called instantiation . Class Object Class is a data type Object is an instance of class It generates OBJECTS It gives life to CLASS Does not occupy memory location It occupies memory locatio It cannot manipulated because it is not available in memory It can be manipulated
- 16. Encapsulation
- 17. • Is the inclusion of property and method within a class/object in which it needs to function property. • Also, enables reusability of an instant of an already implemented class within a new class while hiding and protecting the method and properties from the client classes • The class is kind of a container or capsule or a cell, which encapsulate the set if methods, attributes and properties to provide its indented functionalities to other classes • In that sense, encapsulation also allows a class to change its internal implementation without hurting the overall functioning of the system • That idea of encapsulation is to hide how a class does its operations while allowing requesting its operations
- 18. Example: Let’s say we have a class called “Date”(day, month, year). And then you need to define another class called “Person” that has the following attributes (first name, last name, and birthdate). So in this case we can instantiate an object from class “Date” inside class “Person”
- 19. Encapsulation – Benefits Ensures that structural changes remain local : • Changing the class internals does not affect any code outside of the class • Changing method’s implementation does not reflect the clients using them Encapsulation allows adding some logic when accessing clients data • Example: validation on modifying a property value Hiding implementation details reduces complexity • Easier maintenance
- 20. Inheritance
- 21. • Inheritance – a way of organizing classes • Term comes from inheritance of traits likes eye color, hair color, and so on • Classes with properties in common can be grouped so that their common properties are only defined once in parent class • Superclass – inherit its attributes and methods to the subclass(es) • Subclass – can inherit all its superclass attributes and methods besides having its own unique attributes and methods
- 22. Inheritance allows child classes to inherit the characteristics of existing parent class • Attributes (fields and properties) • Operations (methods) Child class can extend the parent class • Add new fields and methods • Redefine methods (modify existing behavior) A class can implement an interface by providing implementation for all its methods
- 23. Benefits: • Expresses commonality among classes/objects • Allows code reusability • Highlights relationships • Helps in code organization
- 24. Feature 1 Feature 2 Feature 1 Feature 2 ------------------------ Feature 3 Base Class Derived Class (inherited from base class) Features of base class Features of base class accessible to derived class because of inheritance Features defined in derived class
- 25. Example: Person ------------------------------ Name : String Address : String Student ----------------------- School : String ----------------------------- Name : String Address : String Employee --------------------------------- Company : String Salary : double --------------------------------- Name : String Address : String Base class Derived class Derived class
- 26. Vehicle School Bus Sports Car Sedan Luxury Bus Bus Motor Cycle Automobile Super Class Subclasses
- 27. Example: Single Inheritance One class inherits from another Account --------------------- Balance Name Number --------------------- Withdraw Statement Savings Currents Superclass (parent) Subclass (child)
- 28. Example: Multiple Inheritance A class can inherit from several other classes Flying Thing Animal Horse Wolf Bird Helicopter Airplane Multiple Inheritance
- 29. Abstraction: • Abstraction is a design principle • Is the process of removing characteristics from something in order to reduce it to set of essential characteristics. • Through the process of abstraction, a programmer hides all but the relevant data about a class in order to reduce complexity and increase reusability • Abstraction is a basic representation of a concept
- 30. • Abstraction allows programmers to represent complex real world in the simplest manner • It is a process of identifying the relevant qualities and behaviors of an object should possess, in other word represent the necessary features without representing the background details • You should always use abstraction to ease reusability, and understanding for the design and enable extension
- 31. • An abstract class, which declared with the “abstract” keyword, cannot be instantiated • It can only be used as a super-class for other classes that extend the abstract class. • Abstract class is a design concept and implementation gets completed when it is being realized by a subclass.
- 32. Abstraction – types of classes Person Abstract Class Concrete Class Teacher Student Can be instantiated directly DOB: Name: Address: Specialization: Academic Title: Etc…, DOB: Name: Address: GPA: Courses: Etc…, DOB: Name: Address: Can be instantiated directly Can’t be instantiated directly
- 33. • An abstract class is a class that may not have any direct instances. • An abstract operation is an operation that it is incomplete and requires a child to supply an implementation of the operation Shape {abstract} draw() {abstract} Circle draw() Rectangle draw() Abstract class Abstract operation
- 34. Polymorphism: • Encapsulation, Inheritance, and Abstraction concepts are very related to Polymorphism • Polymorphisms is a generic term that means ‘many shapes’. More precisely Polymorphisms means the ability to request that the same methods be performed by a wide range of different types of things • In OOP, polymorphisms is a technical issue and principle • It is achieved by using many different techniques named method overloading, operator overloading, and method overriding
- 35. • An object has “multiple identities”, based on its class inheritance tree • It can be used in different ways Polymorphism – Abstract class: • It is a class that you cannot instantiate from, however, you use it to dominate and specify how the minimum requirements in an inherited classes should be
- 36. public abstract class Robot { public virtual abstract void Move ( ) // abstract move needs } public class LeggedRobot:Robot { public override void Move() { //actions of legged robot to move } } public class WheeledRobot:Robot { public override void Move() { // actions of Wheeled robot to move } } public void moveRobot (Robot A) { A.Move(); } public moveAllRobots() { LeggedRobot lr = new LeggedRobot(); WheeledRobot wr = new WheeledRobot(); moveRobot(lr); moveRobot(wr); }
- 37. Advantages of OOP • Code reuse and recycling • Improved software-development productivity • Improved software maintainability • Faster development • Lower cost of development • Higher-quality software • Encapsulation
- 38. Disadvantages of OOP: • Steep learning curve • Could lead to larger program sizes • Could produce slower programs