Rails: Updating two fields of an ActiveRecord instance simultaniously

Question

I have a model, called Book, that has the fields title and filename (and other fields but they are unrelated). I'd like that the filename field was automatically created using the title, thus in my Book.rb:

class Book < ActiveRecord::Base
  # ...

  def title=(title)
    self.filename = sanitize_filename(title)
    self.title = title
  end

  # ...
end

Because of self.title = title it's going in a infinite recursion. How could I avoid that?

Thanks!

Answer 1

Try this way

class Book
  def title=(title)
    self.filename = sanitize_filename(title)
    self[:title] = title
  end
end

Answer 2

You can write that on before_save

def before_save
  self.filename = sanitize_filename(self.title)
end

Answer 3

There's a section in the ActiveRecord api on 'overwriting default accessors'. The suggested solution there is:

def title=(t)
  self.filename = sanitize_filename(t)
  write_attribute(:title, t)
end