Another aspect of coupling in Object Oriented paradigm

I had previously written a post related to coupling and cohesion here and that was more of a basic definition of both the terms.

In this post I would like to throw some light on the tight dependency on the type of the component in use. Generally we would aim to design classes such that they interact via the interfaces or more generally put via API. Suppose we use interfaces (more of a generic term where we dont have implementations, not specific to keyword interface in Java or C#), but this is not enough, we need to provide some kind of implementation for the interface which is actually consumed by the other client classes.

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SOLID- Open Closed Principle

Open Closed Principle (OCP) states that,

Software entities (Classes, modules, functions) should be OPEN for EXTENSION, CLOSED for MODIFICATION.

Lets try to reflect on the above statement- software entities once written shouldn’t be modified to add new functionality, instead one has to extend the same to add new functionality. In otherwords you don’t touch the existing modules thereby not disturbing the existing functionality, instead you extend the modules to implement the new requirement. So your code is less rigid and fragile and also extensible.

OCP term was coined by Bertnard Meyer.

How can we confirm to OCP principle?

Its simple- Allow the modules (classes) to depend on the abstractions, there by new features can be added by creating new extensions of these abstractions.

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