Hello people,

I have two models with a HABTM association, let´s say book and author.

class Book
  has_and_belongs_to_many :authors
end

class Author
  has_and_belongs_to_many :books
end

The author has a set of attributes (e.g. first-name,last-name,age) that can all be blank (see validation).

validates_length_of :first_name, :maximum => 255, :allow_blank => true, :allow_nil => false

In the books_controller, I do the following to append all authors to a book in one step:

@book = Book.new(params[:book])
@book.authors.build(params[:book][:authors].values)

My question: What would be the easiest way to avoid the saving of authors which fields are all blank to prevent too much "noise" in the database?

At the moment, I do the following:

validate :must_have_some_data

def must_have_some_data
  empty = true
  hash = self.attributes
  hash.delete("created_at")
  hash.delete("updated_at")
  hash.each_value do |value|
    empty = false if value.present?
  end

  if (empty)
    errors.add_to_base("Fields do not contain any data.")
  end
end

Maybe there is an more elegant, Rails-like way to do that.

Thanks.