Question

i’m still new to ruby. i dont understand the methods visibility. the documentation says, all methods are public by default (unless defined otherwise). so this should work (but it doesn’t, MWE):

modules/example.rb:

class Example

  def do_stuff
    puts 'hello world'
  end

end

and testing.rb:

load 'modules/example.rb'

Example.new
Example.do_stuff

calling $ ruby testing.rb
results in

testing.rb:9:in `<main>': undefined method `do_stuff' for Example:Class (NoMethodError)

Can someone explain why? And how to fix it that I can call do_stuff directly?

Answer 1

You are defining an instance method and need to call it on an instance of Example class:

ex_instance = Example.new
ex_instance.do_stuff

If you want to call it directly you need to define it as a class method:

class Example

  def self.do_stuff
    puts 'hello world'
  end

end

then you can call it like this without the need of calling Example.new

Example.do_stuff