Both records must have an id in order to create the has_many

rubyonrails-talk
1

Hi there,

my problem is to add an object to another object through the->through-statement.

product = Product.new product.save p = Product.find(1) catalogue = Catalogue.new calatogue.products

=>

catalogue.products << p

=> ActiveRecord::HasManyThroughCantAssociateNewRecords: Cannot
associate new records through 'Catalogue#catalogue_items' on '#'. Both records must have an id in order to create the has_many :through record associating them.        from

It's exactly was it says. You need to save catalogue first.

Fred

2

Frederick Cheung wrote:

Hi there,

=> ActiveRecord::HasManyThroughCantAssociateNewRecords: Cannot
associate new records through 'Catalogue#catalogue_items' on '#'. Both records must have an id in order to create the has_many :through record associating them.        from

It's exactly was it says. You need to save catalogue first.

I know, but what I don´t understand is:

in the console I do know:

product = Product.new product.save arr = Array.new arr << product catalogue = Catalogue.new(:products => arr) calatogue.products

=> [#<Product id: 1, created_at: "2008-04-28 20:53:34", updated_at: "2008-04-28 20:53:34">]

now i think without saving catalogue first, I have my first product in my catalogue-product-list but:

catalogue.save p catalogue

=> #<Catalogue id: 1, created_at: "2008-04-28 20:55:10", updated_at: "2008-04-28 20:55:10">

catalogue2 = Catalogue.find_by_id(2) p catalogue2.products

=>

shit.... And I don´t know realy why :frowning:

what should I do?!? take catalogue and create a knew empty catalogue2, save this and copy all attributes of catalogue into catalogue2 and save after that catalogue2 again?!? uff.... that´s heavy :frowning:

3

> arr << product > catalogue = Catalogue.new(:products => arr)

This doesn't work. you can only specify attributes in the options to new/create.

what should I do?!? take catalogue and create a knew empty catalogue2, save this and copy all attributes of catalogue into catalogue2 and save after that catalogue2 again?!?

Edge rails (soon to be 2.1) doesn't have this restriction, you could always do that. If not you sill just have to save catalogue2 first before adding to catalogue2.products

Fred

4

That may not actually be true in general.. Definitely true for has_many through though, since in 2.0 that association type has no = method

Fred