Question

I’m working on an internal tool. Here are the three main models im working with:

Site
  has_many Document
    has_many Version

The document model essentially stores a body of content. What I want to do is setup document versioning with the Version model. So the version would store the content.

Right now, I create a new document via the nested URL: POST /sites/:id/documents. Since the form is there, and I have no plans on changing the user experience here, I started building it to use both the Document and Version models. However, I’m starting to feel like this is wrong. Managing validations from a child object and pushing them up to the parent is becoming a pain.

Another note:

The Document has an integer field called active_version_id. It stores the version that is currently the active one of that document. I then use that ID to get the version model, to show the main content connected to that document. I set it to the version created when a document is created.

What i want to do

In short, here’s the workflow I would expect:

1. Goes to create new document
2. Puts in the content
3. Submits the form
4. Parent Document is created.
5. Using the parent document, it creates a new version. Any validation errors on the content at the version level should prevent the save of both models.
6. Errors from the version object should show up on the page, so the user knows.

Here’s my Version model, so you can see the validation logic. It basically checks if the headers in the document are valid (which is just some identification text). And that the headers aren’t used in versions of any other document in that site:

def document_is_in_valid_format
  p = CopyProcess::Processor.new
  if !p.contains_valid_headers(self.content)
    Rails.logger.debug "Headers invalid."
    msg = "Content headers must be in valid format."
    self.document.errors[:base] << msg
    self.errors[:base] << msg
  else
    # Check that headers are unique to the parent document
    headers = content.split(/\n/)[1..3].join(' - ').gsub(/\/\*|\\\*/,'')
    site_documents = []
    # get all documents where it's not this one's parent
    if self.id
      site_documents = Document.where(["site_id = ? AND id <> ?", self.site_id, self.document_id])
    else
      site_documents = Document.where(["site_id = ?", self.site_id])
    end
    site_documents.includes(:versions)
    site_documents.each do |doc|
      if doc.version_names.include?(headers)
        msg = "Content headers are not unique."
        self.document.errors[:base] << msg
        self.errors[:base] << msg
        break
      end
    end
  end
end

I’m wondering if the solution here might be to use a nested form for. For step 5, i imagine a transaction would help prevent both saves.

Answer 1

Check in http://api.rubyonrails.org for:

• validates_associated
• accepts_nested_attributes_for

Also take into account that you can use validations on _id/_ids fields, like validates :document_ids, presence: true to make sure there is at least one document.

To make the code more readable i would try split your long validation sequence in custom validators using:

• ActiveModel::Validator
• ActiveModel::EachValidator