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 endSo, 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 < 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
Image by Freepik If we want to list all the registered users and allow the current user to befriend other users, then we will need to create a new view in the users folder called index.html.erb:-< % @users.each do |user| %>
Now, let's put the controller actions in place. Open the users_controller file and add the index and show methods.
< % 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 ... endWe 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.
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