Std 12 computer chapter 6 object oriented concepts (part 2)
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The document discusses object-oriented programming concepts, specifically focusing on aggregation, composition, and inheritance. Aggregation represents a non-exclusive relationship where parts can exist independently, while composition signifies a strong dependency where the lifespan of component objects is tied to the owner class. Inheritance is highlighted as an 'is-a-kind-of' relationship, allowing subclasses to inherit characteristics from a superclass, promoting reusability and extending functionality.
Std 12 computer chapter 6 object oriented concepts (part 2)
- 1. Object Oriented Concept Part 2 Aggregation & Composition Aggregation vs. Composition Inheritance Composition vs. Inheritance Presented by Nuzhat Ibrahim Memon
- 2. Presented by Nuzhat Ibrahim Memon 2 Name • first name: String • last name: string • display() Person • nm: Name • addr:Address • birthdate:date • setbirthdate(d:int, m:int, y:int):date Address •house: string •street:string •state:string •pincode:int •fulladress(): string Teacher • Subject : string • lecture(d:date, t:time)
- 3. • When objects of one class are composed of objects of other class, it is called aggregation or composition. • It represents “has-a” or “a-part-of” relationship between classes. Presented by Nuzhat Ibrahim Memon 3 Person • nm: Name • addr: Address • birthdate:date • setbirthdate(d:int, m:int, y:int):date • display() Name • First Name: string • Middle name:string • last name:string • fullName():string • display() Address • house: string • street:string • state:string • pincode:int • fulladress(): string • display() Screen • length: int • width: int • model: string Motherboard • model: string • company: string computer • scr: Screen • mb: Motherboard • Take an example of ‘person’ class • We will define two classed ‘Name’ and ‘Address’. • Class ‘Name’ has an attribute first name, middle name and last name. • Class ‘address’ has an attribute house, street, city, state and pincode. • The data type of attributes ‘nm’ and ‘addr’ is class ‘Name’ and ‘Address’ respectively. • Thus class ‘person’ contains object of class ‘Name’ and ‘Address’
- 4. • Aggregation represents non-exclusive relationship between two classes. • In aggregation, the class that forms part of the owner class can exist independently. • The life of an object of the part class is not determined by the owner class. • Object Address may be shared by more than one person. Address is not exclusive to any one person. So, when a person is deleted, the corresponding address cannot be deleted. • Basic aggregation is represented using an empty diamond symbol next to the whole class. • Composition represents exclusive relationship between two classes. • Composition is a strong type of aggregation where the lifetime of the class depends on the existence of the owner class. • If an object of aggregating class is deleted, its part class object also will get deleted. For eg. When an object of class person is deleted, the object of class name is also deleted. Name is associated exclusively with single person. • Composition relationships are represented using a filled diamond next to the whole class. Owner class, Whole class or aggregating class Presented by Nuzhat Ibrahim Memon 4 Name • first name: string • Middle name: string • last name: string • display() Person • nm: Name • addr:Address • birthdate:date • setbirthdate(d:int, m:int, y:int):date Address •house: string •street:string •state:string •pincode:int •fulladress(): string Subject class, part class or aggregated class Subject class, part class or aggregated class Composition Relationship (Filled diamond) Aggregation Relationship (Empty diamond)
- 5. • Inheritance is generally referred to as ‘is-a-kind-of’ relationship between two classes. • Inheritance is appropriate when one class is ‘a kind of’ other class. For e.g. teacher is a kind of person. So, all the attributes and methods of class ‘Person’ are applicable to class ‘Teacher’ also. • Inheritance refers to the capability of defining a new class of objects that inherits the characteristic of another existing class. • In other words, class ‘Teacher’ inherits all attributes and behavior of class ‘Person’. Class ‘Teacher’ may have additional attributes like subject and method like taking lectures of the subject. In such scenario, class ‘Teacher’ can be defined using class ‘Person’. • The feature provides reusability where existing methods can be reused without redefining. In other words, the data attributes and methods of the super class are available to objects in the sub class without rewriting their declarations. Presented by Nuzhat Ibrahim Memon 5 Person • name:string • city: string • gender:char=‘F’ • setBirthdate(d:int, m:int, y:int):date • display() Teacher • subject: string • lecture (d:date, t:time) Existing class is called New Class is called super class sub class parent class child class base class derived class In Class Diagram, Inheritance is represented using an arrow pointing to super class.
- 6. Presented by Nuzhat Ibrahim Memon 6 • Generalization is another name for inheritance or “is a” relationship. • It refers to a relationship between two classes where one class is a specialized version of another. • Common attributes and methods are defined in super class. • Sub class is a specialized version with additional attributes and methods. • There may be a classical hierarchy of inheritance between classes. For e.g. class ‘Employee’ can be derived from class ‘Person’, then class ‘Teacher’ can be derived from ‘Employee’. Here employee is a kind of person and teacher is a kind of employee. Such type of inheritance is known as multilevel inheritance. • A class can also be derived using more than parent classes. For e.g. a child inherits the characteristics of both mother and father. When a class is derived from two or more classes. It is known as multiple inheritance. In multiple inheritance, child will get properties from father as well as mother from both the parents. • Example: airplane is a kind of vehicle as well as flying object. Person Teacher Employee Child Father Mother Airplane Vehicle Flying object Person (Super Class) Teacher (Sub Class) Common attributes & methods Additional attributes & methods Grandfather Son Father
- 7. • In inheritance, class inherits from other classes in order to share, reuse or extend functionality. Here there exists ‘is a’ or ‘a kind of’ relationship between super class and sub class. • In composition, classes do not inherit from other classes, but are ‘composed of’ other classes. Class contains the attributes where some attributes are of objects of other class types. Presented by Nuzhat Ibrahim Memon 7 Social Networking Site Facebook Users is a has a