Ruby Module: Include vs. Extend

ruby_module_include_vs_extend.rb

# Include give you access to a module on a instance level while 
# extend give class level access.

module CanYouHearMe
  def test
    puts "I hear you loud and clear!"
  end
end

class Radio
  include CanYouHearMe
end

class Satellite 
  extend CanYouHearMe
end

# Calling the method test on the class Radio
Radio.test
# Returns
"private method 'test' called for Context::Radio:Class"

# Calling the method test on the class Satellite
Satellite.test
# Returns
"I hear you loud and clear!"

# Calling the method test on an instance of the class Radio
ham_radio = Radio.new
ham_radio.test
# Returns
"I hear you loud and clear!"

# Calling the method test on an instance of the class Satellite
sat_comm = Satellite.new
sat_comm.test
# Returns
"private method 'test' called for #<Context::Satellite:0x000000024ef2f8>"