users_controller.rb

class UsersController < ApplicationController
  def create
    @user = User.new(user_params)

    if @user.save
      #Sends the invitation email using the regular Rails mailers
      AppMailer.welcome_email(@user)

      if params[:invitation_token].present?
        invitation = Invitation.find_by(token: params[:invitation_token])
        # each invitation is associated to the user who issued the invitation
        invitation_user = invitation.user

        # the new user now will follow the invitation user
        @user.leaders << invitation_user

        # the new user is now listed as a follower of the inviations user
        invitation_user.followers << @user

        # stales the invitation so that it can't be used twice
        invitation.update_attribute(:token, nil)

        # rewards the invitation_user for bringing more users yei!
        invitation_user.update_points(500)
      end

      # Inform admins that their milestone has been reached
      if User.count == 50000
        admins = User.where(admin: true)
        AppMailer.community_milestone_reached(admins)
      end

      flash[:success] = "Welcome to Monchitos. Hope you enjoy it!"
      redirect_to posts_path
    else
      flash[:error] = "Sorry your registration could not be completed"
      render :new
    end
  end

  private

  def user_params
    params.require(:user).permit(:email, :name, :username)
  end
end