Forum: Ruby on Rails Returning a record's ID before the record is made?!??

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29a0b45cdf0e6b8b93d520e5105bf4ce?d=identicon&s=25 Michael Kahle (geopoliticus)
on 2008-10-22 07:22
(Received via mailing list)
I am new to Ruby, so apologies.

I'm attempting to combine the input of two objects into one form.  The
objects are customer and registration.  What concerns me is how will I
be able to return the record ID of the customer object to the
registration object so that when the registration object is saved it
contains that customer ID?

I am learning via the book Agile Web Development with Rails (Third
Edition) and in the section on Action view it describes in a section
called "Multiple Models in a Form" a technique used to do this in a
form using the fields_for method.  Then in the registration controller
I would specify the creation of a new customer object in the new
action.  I would also create in the create action of this controller a
transaction to ensure that (from the book)
1. If either model contains invalid data, neither model should be
saved.
2. If both models contain validation errors, we want to display the
messages from both...

I couldn't agree more.  However in the registration object there is a
field called customer_id that has to be populated with the record_id
from the customer model.

How does one get around this?  Thanks for your thoughts in advance.
B14575f0ca69f10938fdd67e7156e0e1?d=identicon&s=25 Craig Demyanovich (Guest)
on 2008-10-22 15:35
(Received via mailing list)
In their example,

def create
  @product = Product.new(params[:product])
  @details = Detail.new(params[:details])
  Product.transaction do
    @product.save!
    @details.product = @product
    @details.save!
    redirect_to :action => :show, :id => @product
  end
rescue ActiveRecord::RecordInvalid => e
  @details.valid? # force checking of errors even if products failed
  render :action => :new
end

they assign the product to the details, @details.product = @product.
When
you do that with related ActiveRecord objects, ActiveRecord takes care
of
setting the IDs for you. In this case, @details.product_id will be set
to @
product.id.

Regards,
Craig
29a0b45cdf0e6b8b93d520e5105bf4ce?d=identicon&s=25 Michael Kahle (geopoliticus)
on 2008-10-23 00:37
Craig Demyanovich wrote:
> In their example,
> ... [snip]
> they assign the product to the details, @details.product = @product.
> When
> you do that with related ActiveRecord objects, ActiveRecord takes care
> of
> setting the IDs for you. In this case, @details.product_id will be set
> to @
> product.id.
>
> Regards,
> Craig

Thanks for your post Craig.  I could not wrap my head around this
concept, partially because it was so difficult for me to implement in
JSP that I resorted to using randomly generated UUID's before inputing
the record into the database.

Active Record to the rescue indeed.  Wow.  I spent about an hour playing
with this last night and was able to magically get this to, well, just
work in Rails.

When I wrote this post originally I hadn't yet tried the example as I
just couldn't understand the code and how it worked.  I took the leap of
faith and followed the example and Ta-da, onto more interesting
problems.

I should also not that another user wrote me off-list and I'd like to
thank him/her for the wonderfully helpful response.  I am not mentioning
his/her name in the event that they wrote off list because they wanted
to remain anonymous.  But thank you.  They suggested I read:
http://railsguides.phusion.nl/activerecord/associa...
and it helped immensely.  I felt like I missed a meeting!

Ruby/Rails has been such a fun experiment thus far.  I'm really loving
it's elegance and simplicity.  Thanks again to all.  TTFN.
D6434aa0b7b350f8c3ed0119d81b2ead?d=identicon&s=25 Roy Pardee (rpardee)
on 2008-10-23 14:28
(Received via mailing list)
You shouldn't have to worry about that.  In this code:

Product.transaction do
  @product.save!               #<-- this saves the product, retrieving
the db-assigned ID
  @details.product = @product  #<-- this writes @product.id to
@details.product_id
  @details.save!               #<-- this saves the @details (since it's
associated w/the product)
  redirect_to :action => :show, :id => @product
end

HTH

-Roy
783700057e363fb4640dfeabd361c31a?d=identicon&s=25 shrink (Guest)
on 2008-12-10 11:13
(Received via mailing list)
On Oct 23, 5:26 pm, "Pardee, Roy" <parde...@ghc.org> wrote:
> You shouldn't have to worry about that.  In this code:
>
> Product.transaction do
>   @product.save!               #<-- this saves the product, retrieving the db-assigned 
ID
>   @details.product = @product  #<-- this writes @product.id to @details.product_id
>   @details.save!               #<-- this saves the @details (since it's associated w/the 
product)
>   redirect_to :action => :show, :id => @product
> end
>
Awesome! Thanks a lot!
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