SOLID s a collection of five common object-oriented development principles collected into one handy acronym. Smart people recommend learning about it, and even the name sounds fantastic! Who doesn't want to write solid code? Clearly, you should strive to follow all five principles, all the time, in all of your code. Right? Well. Good object-oriented design is indeed helpful, but SOLID as a set of guiding principles really isn't. Let's break SOLID down and reveal the limitations of our current approach, and try to understand just how SOLID our code needs to be.