Ayush's Blog

Top Level Functions In Ruby

While working on Matasano crypto challenges, I reached a stage where I could reuse the functions I had written in previous exercises.

So let’s suppose I had a function foo in 1.rb

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def foo
"foo"
end

I need the function foo in my second script named 2.rb

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require_relative "1"

def main
puts 1.x
end

main if __FILE__ == $0

Running the script 2.rb on terminal gives me the error

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$ ruby 2.rb 
2.rb:5:in `main': undefined method `foo’ for 1:Fixnum (NoMethodError)
from 2.rb:8:in `<main>'

This lead me to learning ruby access controls. So the top level methods are private by default and belong to self which is a direct instance of Object itself. This means we can never call these methods with an explicit receiver. In this case, 1 is an explicit receiver which has been imported in 2.rb.

The not-so-good solution I have found for the time being is to mark the required top level function public explicitly.

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public
def foo
"foo"
end

The possible solution might be to use modules, but I am yet to reach that state.