Class Compatibility - Object Oriented Programming - Lecture Slides, Slides of Object Oriented Programming

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Object-Oriented Programming

(OOP)

Lecture No. 6

Class Compatibility

• A class is behaviorally compatible with another if it supports all the operations of the other class
• Such a class is called subtype
• A class can be replaced by its subtype

Example – Class Compatibility

Shape color vertices move setColor draw

Circle radius draw computeArea

Line length draw getLength

Triangle angle draw computeArea

Example – Class Compatibility

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ASCII File … print …

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Polymorphism in OO Model

• In OO model, polymorphism means that different objects can behave in different ways for the same message (stimulus)
• Consequently, sender of a message does not need to know exact class of the receiver

Example – Polymorphism

Shape

Line Circle Triangle draw

draw

draw draw

draw View

Polymorphism – Advantages

• Messages can be interpreted in different ways depending upon the receiver class

Shape

Line Circle Triangle draw

draw

draw draw

draw View

Polymorphism – Advantages

• New classes can be added without changing the existing model

Square draw

Shape

Line Circle Triangle draw

draw

draw draw

draw View