How to notify user when someone follows?

Question

How can we notify a user when he has a new follower?

create_notification is suppose to trigger a notification, but I get different errors with different attempts.

relationship.rb

class Relationship < ActiveRecord::Base
  after_create :create_notification
  has_many :notifications
  belongs_to :follower, class_name: "User"
  belongs_to :followed, class_name: "User"
  validates :follower_id, presence: true
  validates :followed_id, presence: true

private

  def create_notification # How do we need to rewrite this?
    notifications.create(
      followed_id:  followed_id,
      follower_id:  follower_id,  
      user:         follower_id.user,     
      read:         false
    )
  end
end

I used this tutorial as a guide for building my notifications and the Hartl tutorial for building the users and relationships.

relationships_controller.rb

class RelationshipsController < ApplicationController
  before_action :logged_in_user

  def create # The notification is trigger after create.
    @user = User.find(params[:followed_id])
    current_user.follow(@user)
    respond_to do |format|
      format.html { redirect_to @user }
      format.js
    end
  end

  def destroy
    @user = Relationship.find(params[:id]).followed
    current_user.unfollow(@user)
    respond_to do |format|
      format.html { redirect_to @user }
      format.js
    end
  end
end

Sorry my user model is a bit messy.

class User < ActiveRecord::Base
  acts_as_tagger
  acts_as_taggable
  has_many :notifications
  has_many :activities
  has_many :activity_likes
  has_many :liked_activities, through: :activity_likes, class_name: 'Activity', source: :liked_activity
  has_many :liked_comments, through: :comment_likes, class_name: 'Comment', source: :liked_comment
  has_many :valuation_likes
  has_many :habit_likes
  has_many :goal_likes
  has_many :quantified_likes
  has_many :comment_likes
  has_many :authentications
  has_many :habits, dependent: :destroy
  has_many :levels
  has_many :combine_tags
  has_many :valuations, dependent: :destroy
  has_many :comments
  has_many :goals, dependent: :destroy
  has_many :quantifieds, dependent: :destroy
  has_many :results, through: :quantifieds
  has_many :notes
  accepts_nested_attributes_for :habits, :reject_if => :all_blank, :allow_destroy => true
  accepts_nested_attributes_for :notes, :reject_if => :all_blank, :allow_destroy => true
  accepts_nested_attributes_for :quantifieds, :reject_if => :all_blank, :allow_destroy => true
  accepts_nested_attributes_for :results, :reject_if => :all_blank, :allow_destroy => true
  has_many :active_relationships, class_name:  "Relationship",
                                  foreign_key: "follower_id",
                                  dependent:   :destroy
  has_many :passive_relationships, class_name:  "Relationship",
                                   foreign_key: "followed_id",
                                   dependent:   :destroy
  has_many :following, through: :active_relationships,  source: :followed
  has_many :followers, through: :passive_relationships, source: :follower
  attr_accessor :remember_token, :activation_token, :reset_token
  before_save   :downcase_email
  before_create :create_activation_digest
  validates :name,  presence: true, length: { maximum: 50 }
  VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i
  validates :email, presence: true, length: { maximum: 255 },
                    format: { with: VALID_EMAIL_REGEX },
                    uniqueness: { case_sensitive: false }, unless: -> { from_omniauth? }
  has_secure_password
  validates :password, length: { minimum: 6 }
  scope :publish, ->{ where(:conceal => false) }
  User.tag_counts_on(:tags)

  def count_mastered
    @res = habits.reduce(0) do |count, habit|
    habit.current_level == 6 ? count + 1 : count
    end
  end

  def count_challenged
    @challenged_count = habits.count - @res
  end

    def self.from_omniauth(auth)
      where(provider: auth.provider, uid: auth.uid).first_or_initialize.tap do |user|
        user.provider = auth.provider
        user.image = auth.info.image
        user.uid = auth.uid
        user.name = auth.info.name
        user.oauth_token = auth.credentials.token
        user.oauth_expires_at = Time.at(auth.credentials.expires_at)
        user.password = (0...8).map { (65 + rand(26)).chr }.join
        user.email = (0...8).map { (65 + rand(26)).chr }.join+"@mailinator.com"
        user.save!
      end
    end

  def self.koala(auth)
    access_token = auth['token']
    facebook = Koala::Facebook::API.new(access_token)
    facebook.get_object("me?fields=name,picture")
  end


  # Returns the hash digest of the given string.
  def User.digest(string)
    cost = ActiveModel::SecurePassword.min_cost ? BCrypt::Engine::MIN_COST :
                                                  BCrypt::Engine.cost
    BCrypt::Password.create(string, cost: cost)
  end

  # Returns a random token.
  def User.new_token
    SecureRandom.urlsafe_base64
  end

  # Remembers a user in the database for use in persistent sessions.
  def remember
    self.remember_token = User.new_token
    update_attribute(:remember_digest, User.digest(remember_token))
  end

  # Forgets a user. NOT SURE IF I REMOVE
  def forget
    update_attribute(:remember_digest, nil)
  end

  # Returns true if the given token matches the digest.
  def authenticated?(attribute, token)
    digest = send("#{attribute}_digest")
    return false if digest.nil?
    BCrypt::Password.new(digest).is_password?(token)
  end

  # Activates an account.
  def activate
    update_attribute(:activated,    true)
    update_attribute(:activated_at, Time.zone.now)
  end

  # Sends activation email.
  def send_activation_email
    UserMailer.account_activation(self).deliver_now
  end

  def create_reset_digest
    self.reset_token = User.new_token
    update_attribute(:reset_digest,  User.digest(reset_token))
    update_attribute(:reset_sent_at, Time.zone.now)
  end

  # Sends password reset email.
  def send_password_reset_email
    UserMailer.password_reset(self).deliver_now
  end

   # Returns true if a password reset has expired.
  def password_reset_expired?
    reset_sent_at < 2.hours.ago
  end

  def good_results_count
    results.good_count
  end

  # Follows a user.
  def follow(other_user)
    active_relationships.create(followed_id: other_user.id)
  end

  # Unfollows a user.
  def unfollow(other_user)
    active_relationships.find_by(followed_id: other_user.id).destroy
  end

  # Returns true if the current user is following the other user.
  def following?(other_user)
    following.include?(other_user)
  end

private 

    def from_omniauth? 
      provider && uid 
    end

      # Converts email to all lower-case.
    def downcase_email 
      self.email = email.downcase unless from_omniauth? 
    end

    # Creates and assigns the activation token and digest.
    def create_activation_digest
      self.activation_token  = User.new_token
      self.activation_digest = User.digest(activation_token)
    end
end

users_controller.rb

class UsersController < ApplicationController
  before_action :logged_in_user, only: [:index, :edit, :update, :destroy,
                                        :following, :followers]
  before_action :correct_user,   only: [:edit, :update]
  before_action :admin_user,     only: :destroy

  def tag_cloud
    @tags = User.tag_counts_on(:tags)
  end

  def index
    @users = User.paginate(page: params[:page])
  end

  def show
    @user = User.find(params[:id])
    if current_user == @user
      @habits = @user.habits
      @valuations = @user.valuations
      @accomplished_goals = @user.goals.accomplished
      @unaccomplished_goals = @user.goals.unaccomplished
      @averaged_quantifieds = @user.quantifieds.averaged
      @instance_quantifieds = @user.quantifieds.instance
    else
      @habits = @user.habits.publish
      @valuations = @user.valuations.publish
      @accomplished_goals = @user.goals.accomplished.publish
      @unaccomplished_goals = @user.goals.unaccomplished.publish
      @averaged_quantifieds = @user.quantifieds.averaged.publish
      @instance_quantifieds = @user.quantifieds.instance.publish
    end
  end

  def new
    @user = User.new
  end

  def create
    @user = User.new(user_params)
    if @user.save
      @user.send_activation_email
      flash[:info] = "Please check your email to activate your account."
      redirect_to root_url
    else
      render 'new'
    end
  end

  def edit
    @user = User.find(params[:id])
  end

  def update
    @user = User.find(params[:id])
    if @user.update_attributes(user_params)
      flash[:success] = "Profile updated"
      redirect_to @user
    else
      render 'edit'
    end
  end

  def destroy
    User.find(params[:id]).destroy
    flash[:success] = "User deleted"
    redirect_to users_url
  end

  def following
    @title = "Following"
    @user  = User.find(params[:id])
    @users = @user.following.paginate(page: params[:page])
    render 'show_follow'
  end

  def followers
    @title = "Followers"
    @user  = User.find(params[:id])
    @users = @user.followers.paginate(page: params[:page])
    render 'show_follow'
  end

  private

  def user_params
    if params[:conceal] = true
      params.require(:user).permit(:name, :email, :tag_list, :password, :conceal, :password_confirmation, valuations_attributes: [:name, :tag_list, :conceal], activities_attributes: [:conceal, :action, :trackable_id, :trackable_type])
    else
      params[:user][:valuations][:conceal] = false
      params.require(:user).permit(:name, :image, :tag_list, :email, :password, :password_confirmation, valuations_attributes: [:name, :tag_list], activities_attributes: [:action, :trackable_id, :trackable_type])
    end
  end

# Before filters

# Confirms a logged-in user.
    def logged_in_user
      unless logged_in?
        store_location
        flash[:danger] = "Please log in."
        redirect_to login_url
      end
    end

    # Confirms the correct user.
    def correct_user
      @user = User.find(params[:id])
      redirect_to(root_url) unless current_user?(@user)
    end

    # Confirms an admin user.
    def admin_user
      redirect_to(root_url) unless current_user.admin?
    end
end

schema.rb

  create_table "notifications", force: true do |t|
    t.integer  "habit_id"
    t.integer  "quantified_id"
    t.integer  "valuation_id"
    t.integer  "goal_id"
    t.integer  "comment_id"
    t.integer  "user_id"
    t.integer  "habit_like_id"
    t.integer  "quantified_like_id"
    t.integer  "valuation_like_id"
    t.integer  "goal_like_id"
    t.integer  "comment_like_id"
    t.integer  "likes"
    t.integer  "followed_id"
    t.integer  "follower_id"
    t.boolean  "read"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
  end

  create_table "relationships", force: true do |t|
    t.integer  "follower_id"
    t.integer  "followed_id"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
  end

Please let me know if you need further explanation or code :-] Keep the dream alive!

Answer 1

You could simply extend your User#follow method to something like this:

  # Follows a user.
  def follow(other_user)
    active_relationships.create(followed_id: other_user.id)
    UserMailer.new_follower(other_user).deliver_now
  end

Then add a new_follower(user) method to your UserMailer in a similar way than the already existing password_reset method.