Object ID
Object
identity is a property of an object that distinguishes the objects from all
other objects in the applications. With object identity, objects can contain,
or refer to other objects. You can create an object identity in three ways:
1)
You can refer as memory address in programming languages.
2)
Assign identifier keys in the database.
3) By user-specified names, used for both
programming and database. In a complete object oriented system each object is
given an identity that will be permanently associated with the object
irrespective of the object’s structural or state transitions. The identity of
an object is also independent of the location, or address of the object. Object
identity provides the most natural modeling primitive to allow the “same object
to be a sub-object of multiple parent objects”.
Persistency
When
you create an object, it exists for as long as you need it, but under no
circumstances do object exist when the program terminates. While this makes
sense at first, there are situations in which it would be incredibly useful if
an object could exist and hold
its information even while the program is not running. When, next time you
start the program, the object would be there and it would have the same
information it had the previous time the program was running. Of course, you
can get a similar effect by writing the information to a file or to a database,
but in the spirit of making everything an object it would be quite convenient
to be able to declare an object persistent and have all the details taken care
of for you.
0 comments:
Post a Comment
Let us know your responses and feedback