I created a new model named PaypalOrder using:

rails generate model order_id:integer ip_address:string first_name:string last_name:string card_type:string card_expires_on:date

Then I ran rake db:migrate

Now my order model looks like:

class PaypalOrder < ActiveRecord::Base
  belongs_to :order

  attr_accessor :card_number, :card_verification

  validate :validate_card, :on => :create

  def purchase
  #code
  end

  private
  def validate_card
  #code
  end

  def credit_card
  #code
  end

end

and the controller i created:

class PaypalOrdersController < ApplicationController

  def new
    @paypal_order = PaypalOrder.new
  end

  def create
    @paypal_order = current_order.build_paypal_order(params[:paypal_order])
    if @paypal_order.save
      # ...
    else
      render :action => "new"
    end
  end
end

But I'm getting the following error:

NameError in PaypalOrdersController#create

undefined local variable or method `current_order' for #<PaypalOrdersController:0xf7b0a34>

Why am I not able to access the current_order and how can I successfully build paypal_order

EDIT: made the following change:

class PaypalOrdersController < Spree::BaseController

works fine now!!

Why not change line 8 of your controller to:

@paypal_order = PaypalOrder.new(params[:paypal_order])

If it is Rails 4 you'll have to do:

@paypal_order = PaypalOrder.new(params.require(:paypal_order).permit!)