Working With Rails

Let me guess – you only get the error when you create a new record?
id is the primary key and it doesn’t exist when this validation runs. Moreover, why would you need to validate the id? Can the users of your app set the id themselves? If yes, you should definitely change that because the primary key should NEVER be modified!

If you definitely need to do it the way you do (again – I think you’re doing something wrongly if you need to do it) you could always write some kind of safe find method like this:

class MyClass extends ActiveRecord::Base
  def self.safe_find(id)
    raise RecordNotFound, "Couldn't find #{name} without an ID" if id.to_i == 0 # throws an exception like the regular find would
    self.find(id)
  end
end

This raises an error if the id is 0 and otherwise calls the usual find. In your controllers, you can just replace all your normal finds with safe_find so the record can never be displayed, updated or destroyed.

PS: Out of mere curiosity: What do you mean by “control record”?

Hi thanks for that, i don’t get the error only on new.

If I go to the console and try

controlrecord.find(1) I still get the error

The reason I have this record as 0 is because its not used anywhere in the database, and I can easily modify the find kinda like you described above. so it does not show up in a find(:all). But as belt and braces I don’t want the record deleted. Hence..

How about a filter on the model? A before_save filter which returns false if the ID is 0 should stop anyone modifying the record with id = 0. Much cleaner.

David: Good idea but technically that’s not what you’d expect of the app, I guess. If the user accesses a record that (again, technically) isn’t there, I’d expect a 404 which, after all, is exactly what happens if you raise a RecordNotFound exception.

That being said, I still don’t see why a record with pk = 0 should be in the database … Couldn’t you refactor that in a config file?

I haven’t really read much of this, but isn’t validates_numericality_of :id, :on => {:destroy,:update}, :greater_than => 0 supposed to be:
validates_numericality_of :id, :on => [:destroy, :update], :greater_than => 0
?

Clemens, I think you’ve misinterpreted what Colin is trying to do – or at least what I think he is trying to do!

He is saying that he has record, with ID=0, that he doesn’t want the user to be able to alter, no matter what. So refusing to edit a model/record with ID=0 is, by definition, what he wants, right? There is no issue of the record “technically not being there” – it IS there, he just doesn’t want anyone to be able to edit or delete it. Your safe_find method would stop him ever even loading the record with ID=0, which isn’t what he wants.

 class MyModel < ActiveRecord::Base
    before_destroy :protect_record_0
    before_save :protect_record_0

    private
      def protect_record_0
        raise 'trying to modify record with id==0 !!!' if self.id == 0
      end
  end

quick sample from some of my models:

>> c = Country.find_by_name('Marcin')
=> #<Country id: 0, name: "Marcin", code: "mb", lock_version: 0>
>> c.destroy
RuntimeError: trying to modify record with id==0 !!!
        from D:/rails_proj/cv/cv2.0/app/models/country.rb:10:in `protect_record_0'
        from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/callbacks.rb:307:in `send'

[...]

>> c.update_attribute(:name, 'aaa')
RuntimeError: trying to modify record with id==0 !!!
        from D:/rails_proj/cv/cv2.0/app/models/country.rb:10:in `protect_record_0'
        from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/callbacks.rb:307:in `send'
[...]

Hi, Thanks for all the input.

i do need to be able to see the record in a collection, so the safe find method doesn’t work for me.

I’ve gone with Marcins method. I’m very interested to know why my original method doesn’t work. I’ve tried replacing the { with [ but it still doesn’t work

Colin:
I’m not sure why it doesn’t work for the update but the reason for not working with destroy is quite simple: There is no validation on destroy!

Clemens – thats it

if you change it to

validates_numericality_of :id, :on => :update, :greater_than => 0

then it works in the console.

Surely though there should be some method of validating in the destroy method – or am i totally out of date !

No, there is no validation for destroy because it wouldn’t make sense! Validations in ActiveRecord are meant to validate user input – destroy doesn’t take any user input (i.e. there is nothing to update or create) so there is no validation (and there never was, before you ask!).