Document/Paragraph Data Model

doc_instance.rb

def process_paragraphs(paragraphs_attrs)
  paragraphs_attrs.select do |key, value|
    # make changes and filter out existing attributes 
  end
end

def assign_attributes(attr, options = {})
  paragraphs_attrs = attr.delete :paragraphs_attributes
  # manually update any existing paragraphs here
  paragraphs_attrs = process_paragraphs(paragraphs_attrs)

  # pass any new paragraphs onto super
  attr.merge!(paragraphs_attributes: paragraphs_attrs) if paragraphs_attrs

  super(attr, options)
end

instances.rb

class DocInstance
  belongs_to :doc_template
  has_many :paragraph_instances
end

class ParagraphInstance
  belongs_to :doc_instance
  belongs_to :paragraph_template
end

templates.rb

class DocTemplate
  has_many :sections
  has_many :doc_instances
end

class Section
  has_many :paragraphs
end

class ParagraphTemplate
  belongs_to :section
  has_many :paragraph_instances
  attr_accessor :max_length, :required, :title
end