Nested attribute update_attributes uses insert rather than update

Question

I have a user and nested profile class as follows:

class User < ActiveRecord::Base   has_one :profile   attr_accessible :profile_attributes   accepts_nested_attributes_for :profile end  class Profile < ActiveRecord::Base   belongs_to :user   attr_accessible :name end  user = User.find(1) user.profile.id  # => 1 user.update_attributes(profile_attributes: {name: 'some name'}) user.profile.id  # => 2 

I don't understand why rails is throwing away the old profile and creating a new one.

Using

user.profile.update_attributes({name: 'some name'}) 

just updates the current profile as expected. But in that case I'm not taking advantage of accepts_nested_attributes_for

Does anyone know why the update happens this way? I'd prefer not to end up with a database of profile rows not connected to any user.

Answer 1

For everyone who has the same problem in Rails 4: fields_for already adds the id for your nested forms but you have to permit the :id parameter. I only permitted an :object_name_id parameter and since this does not throw any errors it took me some time until i saw this in the server logs. Hopefully this helps someone wasting less time than me on this :)

Answer 2

If you check your form, you need to set the id attribute within the nested attribute hash for your Profile object. If the id is not set, ActiveRecord assumes it's a new object.

For example, if you had an ERB form building a set of 'user' parameters with a nested 'profile_attributes' parameter hash for the nested profile within the user, you could include a hidden value for the profile id, like this:

<%= hidden_field "user[profile_attributes][id]", @profile.id %>