Include two database results in one API request output using Rails 3 - ruby-on-rails-3

Question

I am developing an API in Rails 3 and I got a user model and a message model.
I want the developer to be able to get all info about the user as well as the last message from the user. How can I do this? How can I "include" the messages into the user output?
How can this code be modified to suit my purpose?
def index
#contacts = current_user.contacts
#users = Array.new
#messages = Array.new
#contacts.each do |contact|
user = User.find(contact.friend_id)
#users << user
message = Message.find_by_user_id(contact.friend_id)
#messages << message
end
respond_to do |format|
format.html { render :text => 'Use either JSON or XML' }
format.json { render :json => #users }
format.xml { render :xml => #users }
end
end
Thankful for all input!

Answer 1

You should take advantage of your model, and include the last message as a method in your User model. You can then use the :methods hash of the render method.
format.json { render :json => #users , :methods => [:last_message]}
EDIT
Your user model should be something like:
def User < ActiveRecord::Base
has_many :messages
attr_accessor :name, :email #Include the fields you wish to show here
def last_message
self.messages.first
end
end
And your controller:
def index
#contacts = current_user.contacts
respond_to do |format|
format.html { render :text => 'Use either JSON or XML' }
format.json { render :json => #contacts, :methods => :last_message }
format.xml { render :xml => #contacts, :methods => :last_message }
end
end