28. July 2013 19:32
What is Observer Pattern ?
- Observer Pattern is a Behavioural Pattern which allows one-to-many dependencies between objects so that when one object state changes, all dependent objects can be notified and updated automatically.
- The Observer Pattern is used to implement communication between objects. Since the state of an object (we'll call it subject) is constantly changing, the Observer pattern allows us to define a one to many dependency between other objects (we'll call them observers) to communicate with them letting all the observers know that a subject has changed its state.
- This allows us to notify all observers with a single mechanism.
- The Observer Pattern is set up in the publisher/subscriber pattern, and is excellent for implementing distributed event handling systems and such. This pattern also goes a long way towards removing the coupling between the subject & observer with the use of the IObserver interface.
- The observer design pattern defines a one to many dependency between an object and its dependents. The dependency is created in order to inform the dependents that the object changed its state and therefore the dependents can react to the change.
- A very good example of such behavior is the blogging systems were subscribers are notified whenever a blogger published a new post.
29. June 2013 11:35
Abstraction allows us to represent complex real world in simplest manner. It is process of identifying the relevant qualities and behaviors an object should possess, in other word represent the necessary feature without representing the back ground details. Abstraction is a process of hiding work style of an object and showing only those information which are required to understand the object. Abstraction means putting all the variables and methods in a class which are necessary.
It is a process of hiding all the internal details of an object from the outside real world. The word Encapsulation, like Enclosing into the capsule. It restrict client from seeing its internal view where behavior of the abstraction is implemented. In Encapsulation, generally to hide data making it private and expose public property to access those data from outer world. Encapsulation is a method for protecting data from unwanted access or alteration. Encapsulation is the mechanism by which Abstraction is implemented.
Difference between Abstraction and Encapsulation
Abstraction is a process. It is the act of identifying the relevant qualities and behaviors an object should possess. Encapsulation is the mechanism by which the abstraction is implemented.
|Abstraction solves the problem in the design level.
||Encapsulation solves the problem in the implementation level.
|Abstraction is used for hiding the unwanted data and giving only relevant data.
||Encapsulation is hiding the code and data into a single unit to protect the data from outer world.
|Abstraction is set focus on the object instead of how it does it.
||Encapsulation means hiding the internal details or mechanics of how an object does something.
|Abstraction is outer layout in terms of design.
For Example: - Outer Look of a iPhone, like it has a display screen.
|Encapsulation is inner layout in terms of implementation.
For Example: - Inner Implementation detail of a iPhone, how Display Screen are connect with each other using circuits