Question

I have a form with a nested object (customer < order), and it works except that it keeps creating a new customer record.

I d like to have it check to see if an existing customer is already present in the database (using the customer s email address to search), and if so, just attach the order to the existing record, but if not, continue creating a new customer record.

I think I have to do this by using an before_save call in my order model, but I don t know how to pass the form parameters (email address) in there. Is this the right approach, or is there some other way?

app/models/order.rb:

class Order < ActiveRecord::Base
  belongs_to :customer
  ...
  accepts_nested_attributes_for :customer
  ...
end

app/models/customer.rb:

class Customer < ActiveRecord::Base
  has_many :orders
  ...
end

app/controllers/orders_controller.rb:

def new
  @order = Order.new
  @order_number = "SL-#{Time.now.to_i}"
  @order.customer = Customer.new
  @services_available = Service.all
end

def create
  @order = Order.new params[:order]

  if @order.save
    flash[:notice] =  Order was successfully created. 
    redirect_to @order
  else
    @order_number = "SL-#{Time.now.to_i}"
    render :action => "new"
  end
end

app/views/order/new.html.haml:

%h1 New order
- form_for @order do |order_form| 
  = error_messages_for :order
  %p
    = order_form.label :order_number
    %br
    = text_field_tag   , @order_number, :disabled => true, :id =>  order_number_display 
    = order_form.hidden_field :order_number, :value => @order_number
  - order_form.fields_for :customer do |customer_form| 
    %p
      = customer_form.label :first_name
      %br
      = customer_form.text_field :first_name
    %p
      = customer_form.label :last_name
      %br
      = customer_form.text_field :last_name
    %p
      = customer_form.label :phone
      %br
      = customer_form.text_field :phone
    %p
      = customer_form.label :email
      %br
      = customer_form.text_field :email
  %p= order_form.submit  Create Order 
= link_to  Back , orders_path

Answer 1

With accepts_nested_attributes_for the attributes for the nest model are passed in the params has with the key :model(s)_attributes in your case: params[:order][:customer_attributes]

Because you have the accepts_nested_attributes_for works on the belongs_to side of a one-to-many relationship you re going to have to do some extra work. By overriding the customer_attributes attr_writter created when you call accept_nested_attributes_for.

In short this should work, or at least help you figure it out:

class Order < ActiveRecord::Base
  accepts_nested_attributes_for :customer
  belongs_to :customer


  def customer_attributes_with_existence_check=(attributes)
    self.customer = Customer.find_by_email(attributes[:email])
    self.customer_attributes_without_existence_check=(attributes) if customer.nil?
  end

  alias_method_chain  customer_attributes= , :existence_check

end

Answer 2

adding

update_only => true

to

accepts_nested_attributes_for :[model]

will not destroy the nested model each time.

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