This community-built FAQ covers the “What’s a Module?” exercise from the lesson “Object-Oriented Programming II”.
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This exercise can be found in the following Codecademy content:
Learn Ruby
FAQs on the exercise What’s a Module?
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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.
