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Slide 1: Information Hiding(OOP) http://ecomputernotes.com
Slide 2: Information Hiding ►Information ►It ►It is stored within the object is hidden from the outside world can only be manipulated by the object itself http://ecomputernotes.com
Slide 3: Example – Information Hiding ►Ali’s ►We name is stored within his brain can’t access his name directly we can ask him to tell his name ►Rather http://ecomputernotes.com
Slide 4: Example – Information Hiding ►A phone stores several phone numbers can’t read the numbers directly from the SIM card ►We ►Rather phone-set reads this information for us http://ecomputernotes.com
Slide 5: Information Hiding Advantages ►Simplifies the model by hiding implementation details ►It is a barrier against change propagation http://ecomputernotes.com
Slide 6: Encapsulation ►Data and behaviour are tightly coupled inside an object ►Both the information structure and implementation details of its operations are hidden from the outer world http://ecomputernotes.com
Slide 7: Example – Encapsulation stores his personal information and knows how to translate it to the desired language ►Ali ►We don’t know How the data is stored How Ali translates this information http://ecomputernotes.com
Slide 8: Example – Encapsulation Phone stores phone numbers in digital format and knows how to convert it into humanreadable characters ►A ►We don’t know How the data is stored How it is converted to human-readable characters http://ecomputernotes.com
Slide 9: Encapsulation – Advantages ►Simplicity ►Low and clarity complexity understanding ►Better http://ecomputernotes.com
Slide 10: Object has an Interface object encapsulates data and behaviour ►So how objects interact with each other? ►Each object provides an interface (operations) ►Other objects communicate through this interface ►An http://ecomputernotes.com
Slide 11: Example – Interface of a Car ►Steer Wheels ►Accelerate Gear ►Apply Brakes ►Turn Lights On/Off ►Change http://ecomputernotes.com
Slide 12: Example – Interface of a Phone Number ►Place Call ►Disconnect Call ►Add number to address book ►Remove number ►Update number ►Input http://ecomputernotes.com
Slide 13: Implementation ►Provides ►This services offered by the object interface includes Data structures to hold object state Functionality that provides required services http://ecomputernotes.com
Slide 14: Example – Implementation of Gear Box ►Data Structure Mechanical structure of gear box ►Functionality Mechanism to change gear http://ecomputernotes.com
Slide 15: Example – Implementation of Address Book in a Phone ►Data Structure SIM card ►Functionality Read/write circuitry http://ecomputernotes.com
Slide 16: Separation of Interface & Implementation change in implementation does not effect object interface ►Means is achieved via principles of information hiding and encapsulation ►This http://ecomputernotes.com
Slide 17: Example – Separation of Interface & Implementation driver can drive a car independent of engine type (petrol, diesel) ►A interface does not change with the implementation ►Because http://ecomputernotes.com
Slide 18: Example – Separation of Interface & Implementation driver can apply brakes independent of brakes type (simple, disk) ►A ►Again, reason is the same interface http://ecomputernotes.com
Slide 19: Advantages of Separation need not to worry about a change until the interface is same ►Users ►Low Complexity access to information structure of an object can produce errors ►Direct http://ecomputernotes.com
Slide 20: Messages communicate through messages ►They send messages (stimuli) by invoking appropriate operations on the target object ►The number and kind of messages that can be sent to an object depends upon its interface ►Objects http://ecomputernotes.com
Slide 21: Examples – Messages Person sends message (stimulus) “stop” to a Car by applying brakes ►A Person sends message “place call” to a Phone by pressing appropriate button ►A http://ecomputernotes.com