gistfile1.rb

# power of extend

# can be used to add methods only to top-level object
module Rake
  def task
    :executed
  end
end

extend Rake
task # => :executed
Object.new.task # => NoMethodError


# respects method visibility scopes contrary to module_function
module Friends
  extend self
  
  def joey
    "how're you doing"
  end

  private

  def rachel
    "i'm nacked, get out"
  end
end

Friends.joey # => how're you doing
# if we'd used module_function instead of extend self then next lines would return NoMethodError
Friends.rachel # private method `rachel' called for Friends:Module
Friends.send(:rachel) # => i'm nacked, get out