Model User

class User < ApplicationRecord

attr_accessor :registration

  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
end

Controler Application

class ApplicationController < ActionController::Base
  attr_reader :current_user

private
  before_filter :configure_devise_params, if: :devise_controller?
  def configure_devise_params
    devise_parameter_sanitizer.for(:sign_up) do |u|
      u.permit(:registration, :email, :password,  :password_confirmation)
    end

  end

  protected
  def authenticate_request!
    unless user_id_in_token?
      render json: { errors: ['Not Authenticated'] }, status: :unauthorized
      return
    end
    @current_user = User.find(auth_token[:user_id])
  rescue JWT::VerificationError, JWT::DecodeError
    render json: { errors: ['Not Authenticated'] }, status: :unauthorized
  end

  private
  def http_token
      @http_token ||= if request.headers['Authorization'].present?
        request.headers['Authorization'].split(' ').last
      end
  end

  def auth_token
    @auth_token ||= JsonWebToken.decode(http_token)
  end

  def user_id_in_token?
    http_token && auth_token && auth_token[:user_id].to_i
  end
end

u = User.new(email:'a@a.com', registration:192536, password:'changeme', password_confirmation:'changeme')

=> #<User id: nil, email: "a@a.com", registration: nil>