A Simple Twitter App with Ruby on Rails – Building Friendships
Introduction
This is the third and final part of series on how to create a twitter style web application with Ruby on Rails. This part will cover how to add friendships between users.- The first part of this tutorial: A Simple Twitter App with Ruby on Rails – Messages With Ajax
- The second part of this tutorial: A Simple Twitter App with Ruby on Rails – User Authentication
Self-Referential Relationship
Image by pikisuperstar on Freepik
To create friendships between users we have to deal with a special type of association, which is called a self referential relationship. It is called this because the model (in this case, User) references itself. Why? Well if a given "user" has many "friends", those "friends" are also "users". Furthermore, each of those friends can also have friends, so we are dealing with a many to many relationship. The relationship can affectively be called a "friendship" because friendships can be gained and lost (as in real life). So, let's create the friendship model with two foreign keys.> ruby script/generate model friendship user_id:integer friend_id:integerNow, migrate the database:-
> rake db:migrate
Making and Losing Friends
Image by standret on Freepik
We will need to create and destroy friendships and for this we will need a controller for friendships:-> ruby script/generate controller friendshipsNow add the create and destroy methods as shown below:-
class FriendshipsController < ApplicationController
def create
@friendship = current_user.friendships.build(:friend_id => params[:friend_id])
if @friendship.save
flash[:notice] = "Added friend."
redirect_to root_url
else
flash[:error] = "Error occurred when adding friend."
redirect_to root_url
end
end
def destroy
@friendship = current_user.friendships.find(params[:id])
@friendship.destroy
flash[:notice] = "Successfully destroyed friendship."
redirect_to root_url
end
end
class Friendship < ActiveRecord::Base ... belongs_to :friend, :class_name => "User" endWe need to add two lines to the User model. A User has many friendships and has many friends through friendships. This reads almost exactly as it is coded, which is a testament to Ruby on Rails.
class User < ActiveRecord::Base has_many :friendships has_many :friends, :through => :friendships ... end
Listing your Friends
< % @users.each do |user| %>
< % if user.username != current_user.username %> < %=h user.username %> < %= link_to "Add Friend", friendships_path(:friend_id => user), :method => :post %> < % end %>
< % end %>
class UsersController < ApplicationController
def index
@users = User.all
end
def show
@user = current_user
end
...
end
We need to do two more things before we can give this a whirl. First add the friendships resource to the routes file:-
map.resources :friendships...and finally, we can add some links on the posts/index.html.erb file:-
...< %= link_to "Make Friends", users_path %> < %= link_to "My Friends", { :controller => "users", :action => "show", :id => current_user } %> Ok, we can now start up the server and browse to http://localhost:3000 to have a look.
Summary
Obviously there are several directions you could take this application. A lot of features could be added and it could be spruced up, somewhat. I hope these tutorials have helped you in some way and again, I would highly recommend that you try Ruby on Rails, if you haven't already.
Author: Phil McClure
Phil McClure is a Software Developer from Belfast, Northern Ireland. His main interests are software architecture, design patterns and how these can be applied to web development. Phil blogs at Therailworld. Follow him on Twitter.Write for Us! We are looking for exciting and creative articles, if you want to contribute, just send us an email.
Beautiful code. and very well written tutorial.
Thanks.
I just finished doing some analysis on modeling friendships myself. Here are a few other resources I found useful:
swemoney’s has_many_friends plugin, which while no longer in active development, is worth reviewing the source code for some ideas for convenience methods and an alternative association model.
http://github.com/swemoney/has_many_friends/tree/master
There is also a few excellent questions on stackoverflow addressing this scenario:
http://stackoverflow.com/questions/623909/rails-model-with-foreignkey-and-link-table/623956#624261
http://stackoverflow.com/questions/1071014/rails-two-way-friendship-model-contd
And, of course, Ryan Bates’ railscast:
http://railscasts.com/episodes/163-self-referential-association
Don’t work in rails but interesting tutorial nonetheless. Code is quite clear.
Thanks, simple and well explained.
how to upgrate my photoshop skill.
Every new idea is a new reflexion i will google it
helpful tutorial. Thanks.
nice!!
Tutorial added to TheWebTuts
Is there something missing in this tut?
Where did you write “Find New Friends”?
Can you post the code for /users/show.html.erb it’s not in the tutorial
nevermind found it here
http://github.com/overture8/Twitter-Blog-Demo/blob/master/app/views/users/show.html.erb
you need to create /users/show.html.erb file and code is:
Username:
Friends
– :delete %>
Wow this is a great tutorial, thanks.
One thing though, i noticed i can add the same friend twice. I want to make it so when i go to add friends if a friendship exists then it doesn’t display the friend when i go to find new friends or when i click the add friend it flash[:notice] = “that user is already your friend”. Im assuming this would probably go in the controller but i dont know how to check if a friendship exists.
lol.. just check in if that user is on the array of users
hi,
same question with mike.
kindly please help me. thanks. :)
Pretty good tutorial, I’m used to Ruby but I’m starting in Rails and this is really a must for starters, it takes you all the way and (i did) let’s you add more things on the go. Some of the code is missing in all tutorials though, makes it hard to follow and sometimes is not easy to figure it out yourself.
So, what exactly do we relate the user model to?? Well, first we need to specify that the friendship model belongs to a friend (which is actually a user!). You can do this by adding some more lines to the user model:-
class Friendship “User”
end
i think u have misplaced user model instead friendship model ..
The problem I see with this method is that friendships are reciprocal. So, if user 1 is listed as friends with user 2 then user 2 must also be friends with user 1. Creating another database entry for this seems redundant. How would you handle this?
No it is not redundant. because each row is unique. (Row #1) has user2 as user1’s follower. (Row #2) If they follow each other : user1 as user2’s follower. Easy and simple. (think of difference in facebook and twitter.. in facebook u have to confirm friendship, in twitter u dont)
I’ve worked through this tutorial and got it all working but I want to add a feature and i can’t work out how to do it:
I’m able to get a list of the people a person is following. But I can’t work out how to get a list of the people following a person…
that only shows the people being follow by a user…
I have looked at the SQL table and its storing the links with the user_id and the friend_id… so the above code looks for all records where the @user.id is = to user_id in the table…
I need to be able to access all the records where friend_id = @user.id to get a list of people following the user…
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The action ‘index’ could not be found for FriendshipsController, dont know why i keep having this issue, im using Rails 3