Summary

The SOLID principles are key guidelines for good object-oriented software design.

Building software is an incredibly hard task—the logic of the code is complex, its behavior at runtime is hard (if even possible, sometimes) to predict, requirements change constantly as well as the environment, and there are multiple things that can go wrong.

In addition, there are multiple ways of constructing software with different techniques, paradigms, or tools, which can work together to solve a particular problem in a specific manner. However, not all of these approaches will prove to be correct as time passes, and requirements change or evolve. However, by this time, it will already be too late to do something about an incorrect design, as it is rigid, inflexible, and therefore hard to change a refactor into the proper solution.

This means that, if we get the design wrong, it will cost us a lot in the future. How can we then achieve a good design that will...