has_many validation the Rails way

Okay, this is something I run into a lot and don't really have a great solution. Here is a simple example:

class Blog < ActiveRecord::Base   has_many :posts   validates_presence_of :name end

class Post < ActiveRecord::Base   belongs_to :blog   validates_presence_of :name   validates_presence_of :blog_id end

Now, if I want to create a blog and post at the same time I don't want either to be created if one of them fails. So imagine that I have a new valid blog, but a post with no name. I do not want the blog to be created because the post failed validation.

Thanks, Tom

Is this the multiple-models-one-form problem? If so, see this & the prior 2 railscasts:

The problem that's not treated in those (IIRC) is how to give informative error messages when child item validation fails. IIRC, you get *something* but it's not super informative...




I have probably 3 different solutions I've used in different places, but they each have different drawbacks. The closest solution is the one you refer to, where when the child validates it has an error on the required parent_id, but the parent_id is only missing because the child failed validation!

Any beautiful solutions out there?

Thanks, Tom