how to show 'recently visited'? - ruby-on-rails

Question

I have created a web app that has user profiles, where users can search for fellow users based on interests, as well as post + attend events etc.. How might I add a feature where users can see who 'Recently visited' a certain event?
event.rb
class Event < ActiveRecord::Base
attr_accessible :title, :description, :location, :date, :time, :event_date
acts_as_commentable
has_many :comments, as: :commentable
belongs_to :user
has_many :event_participants, dependent: :destroy
has_many :participants, through: :event_participants, source: :user
end
user.rb
class User < ActiveRecord::Base
include PgSearch
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable, :omniauthable,
:omniauth_providers => [:facebook, :twitter, :linkedin]
attr_accessible :email, :password, :password_confirmation, :zip, :gender, :remember_me, :first_name, :last_name,
:birthday, :current_password, :occupation, :address, :interests, :aboutme, :profile_image,
:photos_attributes, :age, :education, :ethnicity
has_many :authorizations, :dependent => :destroy
has_many :comments
has_many :events
has_many :photos, as: :attachable
has_many :questions
has_many :sent_messages, class_name: 'Message', foreign_key: :sender_id
has_many :received_messages, class_name: 'Message', foreign_key: :receiver_id
accepts_nested_attributes_for :photos
mount_uploader :profile_image, ProfileImageUploader
end
event_participants.rb
class EventParticipant < ActiveRecord::Base
attr_accessible :user_id, :event_id
belongs_to :user
belongs_to :event
validates :user_id, uniqueness: {scope: :event_id}
end
events_controller snippit
class EventsController < ApplicationController
before_filter :authenticate_user!
def index
#users = User.all
#user = current_user
#events = Event.all
#interesting_people = #users.order("random()").first(5)
end
def new
#event = Event.new
end
def create
#event = current_user.events.new(event_params)
respond_to do |format|
if #event.save
format.html { redirect_to :back, notice: 'Event was successfully created.' }
format.json { render action: 'show', status: :created, location: #event }
format.js
else
format.html { render action: 'new' }
format.json { render json: #event.errors, status: :unprocessable_entity }
format.js
end
end
end
def show
#users = User.all
#user = current_user
#event = Event.find(params[:id])
#commentable = #event
#comment = #event.comments.new
#interesting_people = #users.order("random()").first(5)
end

Answer 1

Based on your code, it looks like you could do something like:
#event.event_participants.include(:users).order('created_at desc').limit(X).map(&:user)
You could also try without the include:
#event.event_participants.order('created_at desc').limit(X).map(&:user)
But that will do N+1 queries. The join will perform better.
Where in the above code, X would be how many participants you want to show.