Open/Closed principle states "software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification"; that is, such an entity can allow its behaviour to be extended without modifying its code.

State Machines are useful for tracking the state of an object. With AASM, we take a dive into how states can transition as well as modifying states and interacting with them.

There is a lot of work that is done on new applications and a lot of the common code between new applications. In this episode, we look at using templates to speed up the initial process.

In this episode, we look at the Liskov Substitution Principle. If S is a subtype of T, then objects of type T may be replaced with objects of type S without altering any of the desirable properties of the program.

Let's face it, Ruby is slow , but don't abandon Ruby just yet. Using extensions, we can write performant code in another language for the specific slow functions while the rest of the application remains untouched.