SOLID

I bet you have encountered some code smells during your programming career.

Maybe you have made a change (corrected a bug) in a module, which caused a change (introduced a new bug) in another unforseen module?

Maybe you have experienced that a very simple change in your module will force you to do changes in multiple modules?

Even worse, code duplicates you wasn't aware of (you fixed a bug in a function in a module, but the bug was not fully solved due an exact code duplicate of the function in another module)?

There are more code smells around out there, you tell me!

However, using SOLID will help you to prevent some of the code smells. SOLID is a set of five basic OOP principles, that will help you to write quality software.

The SOLID acronym:

S : Single responsibility principle (SRP)
   There should never be more than one reason for a class to change

O : Opened/closed principle (OCP)
   Software entities should be open for extension, but closed for modification

L : Liskov substitution principle (LSP)
   Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it

I : Interface segregation principle (ISP)
   Clients should not be forced to depend upon interfaces that they do not use

D: Dependency inversion principle (DIP)
   A. High level modules should not depend upon low level modules. Both should depend upon abstractions.
B. Abstractions should not depend upon details. Details should depend upon abstractions

There is a lot of good articles on the net. I have no intention to explain them here. This post is more of a reminder that there are basic principles to follow.

My personal experienced is that you will need some training to actually understand when to use them. Further you will need some time to make it a habit to always consider SOLID when you are writing software.

Generally, I think it is easier to use SOLID when writing new software. To apply SOLID in existing code demands more effort (and time). Of course, it depends on the code you start from.

You are welcome to leave comments, complaints or questions!