FAQ: Object-Oriented Programming II - What's a Module?

This community-built FAQ covers the “What’s a Module?” exercise from the lesson “Object-Oriented Programming II”.

Paths and Courses
This exercise can be found in the following Codecademy content:

Learn Ruby

FAQs on the exercise What’s a Module?

There are currently no frequently asked questions associated with this exercise – that’s where you come in! You can contribute to this section by offering your own questions, answers, or clarifications on this exercise. Ask or answer a question by clicking reply (reply) below.

If you’ve had an “aha” moment about the concepts, formatting, syntax, or anything else with this exercise, consider sharing those insights! Teaching others and answering their questions is one of the best ways to learn and stay sharp.

Join the Discussion. Help a fellow learner on their journey.

Ask or answer a question about this exercise by clicking reply (reply) below!

Agree with a comment or answer? Like (like) to up-vote the contribution!

Need broader help or resources? Head here.

Looking for motivation to keep learning? Join our wider discussions.

Learn more about how to use this guide.

Found a bug? Report it!

Have a question about your account or billing? Reach out to our customer support team!

None of the above? Find out where to ask other questions here!

Check out our example module in the editor. See how it has an approximation of pi stored in PI and a series of methods for calculating the circumference and area of a circle?

Click Next to continue.

When I ran the example module in the editor this was the message recd.

(ruby):2: warning: already initialized constant Context::Circle::PI
(ruby):2: warning: previous definition of PI was here.

No warning will be shown the first time you run it. The warning only pops afterwards, as explained in the next exercise:

Ruby doesn’t make you keep the same value for a constant once it’s initialized, but it will warn you if you try to change it.
We created our own PI in the previous exercise, but don’t worry: because they’re in separate modules, Ruby knows to keep them separate.

Because the compiler has recorded PI and if you run the block after the first time, you are basically repeating the definition of PI (no matter it is the same value or not), thus Ruby would show warning - it does not stop the programme running though.

You can test it with a puts method like this (after initialising PI):

module Circle PI = 3.141592653589793 def Circle.area(radius) PI * radius**2 end def Circle.circumference(radius) 2 * PI * radius end end puts Circle.area(2)

To stop the warning message, just simply remove the PI = 3.141592653589793 line.