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OOPs beyond the Four Pillars - SOLID and GRASP

As we know Object oriented programming is a type of programming paradigm based around programming classes and instances of classes called objects. These can be objects that appear on the screen (e.g., pictures, textboxes, etc.) or are part of the programming (e.g. actors, connections, particles, etc as mentioned in my post http://www.developerscloud.org/2013/02/what-is-oop-basic-concepts.html written ages ago.

 Here we are going to extend the oops beyond its four pillars i.e.
  1. Abstraction
  2. Encapsulation
  3. Polymorphism and
  4. Interfaces i.e. Inheritance


 So first we will go through SOLID and then GRASP

SOLID Principles are principles of class design.

•SRP: Single Responsibility Principle
–An object should have only a single responsibility & all the responsibility should be entirely encapsulated by the class.
–There should never be more than one reason for a class to change
•OCP: Open/Closed Principle
–Software entities should be open for extension, but closed for modification
•LSP: Liskov Substituion Principle
–Objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program
•ISP: Interface Segregation Principle
–many client specific interfaces are better than one general purpose interface
–once an interface has gotten too 'fat' split it into smaller and more specific interfaces so that any clients of the interface will only know about the methods that pertain to them. No client should be forced to depend on methods it does not use
•DIP: Dependency Inversion Principle
–Depend upon Abstractions. Do not depend upon concretions.

–Dependency Injection (DI) is one method of following this principle.

 GRASP


•Acronym for General Responsibility Assignment Software Patterns.
•Assigning responsibilities to classes is a critical aspect of object-oriented design.
•Appropriate assignment of responsibilities to classes is the key to successful design.
•There are fundamental principles in assigning responsibilities that experienced designers apply.
•These principles are summarized in the GRASP patterns.
•Has nine core principles that object-oriented designers apply when assigning responsibilities to classes and designing message interactions.


Nine Principles:
•Expert.
•Creator.
•Controller.
•Low Coupling.
•High Cohesion.
•Polymorphism.
•Pure Fabrication.
•Indirection.
•Don’t Talk to Strangers.

I think this article is not so great in terms of visualizations but indeed if you read it, it will help you to brush up your concepts and increase your productivity as well...
In Continuation Next Post: http://www.developerscloud.org/2014/09/extending-object-oriented-programming.html

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Location: Bengaluru, Karnataka, India

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