event_01.rb

require_relative './event_emitter_core'

class EventEmitter
  include EventEmitterCore
end

event_emitter = EventEmitter.new

# the code should be executed when event will be triggered
ring_bell = lambda do |event_name, object|
  puts 'ring ring ring'
end

# create an event 'doorOpen'
event_emitter.on(:doorOpen)

# and subscribe code to event
event_emitter.subscribe(:doorOpen, ring_bell)

# to trigger event
event_emitter.emit(:doorOpen)
# 'ring ring ring'