Reflection

Ruby is a very permissive language, as you’ve already seen time and time again. It allows developers to open any class, add new methods, remove others, include mixins, and more. Ruby isn’t satisfied with just that, and so it provides some impressive reflection capabilities.

Reflection means that the code can investigate itself and its environment. Hence, you can retrieve a list of current defined variables, check what the superclass of an object is, and more. This gives you a lot of control over objects during the runtime of the application.