In this chapter, we went through software guides and patterns. We started with the SOLID principles proposed by Robert Martin a few years ago, which are now gaining momentum among the programmers community, and we can see them implemented in the vast majority of frameworks in use today.

We used a simple application, and as the requirements evolved, we applied different principles or patterns to solve the problems.

Finally, we studied the eight most used GoF patterns (according to the statistics), revising their definitions and purposes in order to finish with the current list of available patterns created and published after the GoF group published their book.

In the next chapter, we'll deal with security issues, including the new proposals widely adopted in the industry, such as the OAuth (Open Authorization) protocol.