Enforcing uniqueness constraints

[vgarcia]

Okay, let's assume I have two database tables, pages and sections. Each page belongs to a section. Each section cannot have two pages with the same filename. Let's assume this is my page model class:

class Page < ActiveRecord::Base
  validates_uniqueness_of 	:filename

  validates_presence_of 	:page_title
  validates_presence_of		:page_content
end

Now, my "validates_uniqueness_of" constraint somewhat works, but for example I can only have one page named "index" regardless of how many sections I have. How would I enforce the rule that the combination of section_id and filename must be unique, rather than just one or the other?

[Luke Redpath]

I'm not sure if there is a way to easily to do this using Rails' quick and easy helpers - as good and useful as they are, any form of medium to complex validation is probably best done using the validation methods:

class Page < ActiveRecord::Base
  validates_presence_of      :page_title
  validates_presence_of      :page_content

  def validate
    # check for an existing filename/section_id combo here
  end
end

[Luke Redpath]

Scrap that, what you want is the :scope option.

  validates_uniqueness_of      :filename, :scope => 'section_id'

Just found this in the API docs. Don't you just love rails

[vgarcia]

Very cool Luke . I'm off to do some JSP work now but I'll revisit this later tonight

[Luke Redpath]

Did this work for you in the end Vinnie?

[vgarcia]

Did this work for you in the end Vinnie?

I haven't been able to get back to it unfortunately (I've been working on the project, but other parts of it) . I'm hoping this weekend will give me more time to work on this.

[vgarcia]

Coming back to this now, and it's definitely working! Thanks for the help Luke