Installation

# Gemfile
gem 'has_friends'

Then run bundle. Alternatively

gem install has_friends

Then you need add has_friends method to your User model and generate friendship migration with

has_friends install

and run rake db:migrate in order to migrate the new generated migration. Case your User model has no friends_count column in it's table, you can easily generate a migration to accomplish this with

has_friends counter

and run rake db:migrate again.

Usage

Add the method call has_friends to your model.

  class User < ActiveRecord::Base
    has_friends
  end

Common tasks

  john = User.find_by_login 'john'
  mary = User.find_by_login 'mary'
  paul = User.find_by_login 'paul'

  # john wants to be friend with mary
  # always return a friendship object
  john.be_friends_with(mary)

  # are they friends?
  john.friends?(mary)

  # get the friendship object
  john.friendship_for(mary)

  # mary accepts john's request if it exists;
  # makes a friendship request otherwise.
  mary.be_friends_with(john)

  # check if paul is mary's friend
  mary.friends?(paul)

  # check if an user is the current user, so it can
  # be differently presented
  mary.friends.each {|friend| friend.is?(current_user) }

  # if you're dealing with a friendship object,
  # the following methods are available
  friendship.accept!

  # if you're using has_paginate plugin, you can use it:
  mary.friends.paginate(:page => 3, :limit => 10)

  # the be_friends_with method returns 2 params: friendship object and status.
  # the friendship object will be present only when the friendship is created
  # (that is, when is requested for the first time)
  # STATUS_ALREADY_FRIENDS     # => users are already friends
  # STATUS_ALREADY_REQUESTED     # => user has already requested friendship
  # STATUS_IS_YOU          # => user is trying add himself as friend
  # STATUS_FRIEND_IS_REQUIRED      # => friend argument is missing
  # STATUS_FRIENDSHIP_ACCEPTED     # => friendship has been accepted
  # STATUS_REQUESTED         # => friendship has been requested

  friendship, status = mary.be_friends_with(john)

  if status == Friends::STATUS_REQUESTED
    # the friendship has been requested
    Mailer.deliver_friendship_request(friendship)
  elsif status == Friends::STATUS_ALREADY_FRIENDS
    # they're already friends
  else
    # ...
  end

Generated Migrations

  class CreateFriendships < ActiveRecord::Migration
    def self.up
      create_table :friendships do |t|
        t.references :user, :friend
        t.datetime :requested_at, :accepted_at, :null => true, :default => nil
        t.string :status
      end

      add_index :friendships, :user_id
      add_index :friendships, :friend_id
      add_index :friendships, :status
    end

    def self.down
      drop_table :friendships
    end
  end

  class AddFriendsCountToUser < ActiveRecord::Migration
    def self.up
      add_column :users, :friends_count, :integer, :default => 0, :null => false
    end

    def self.down
      remove_column :users, :friends_count
    end
  end

LICENSE:

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.