Ruby module_functions demo

module_functions.rb

module A
  module_function

  def a
    'I am a'
  end

  def b
    'I am b'
  end
end

# module_function provides an easy way to define functions with the module as a receiver
# No need for `extend ClassMethods` or reopening classes
puts A.a
puts A.b

class C
  # Including a module that has functions defined with module_function _copies_ them in as private
  # instance methods
  include A
end

puts C.respond_to? :a
puts C.respond_to? :b
c = C.new
puts c.respond_to? :a
puts c.respond_to? :b
puts c.send(:a)
puts c.send(:b)

class D
  # Extending a module that has functions defined with module_function
  extend A
end

puts D.respond_to? :a
puts D.respond_to? :b
puts D.send(:a)
puts D.send(:b)
d = D.new
puts d.respond_to? :a
puts d.respond_to? :b