Rails - Feb 2008 - validates_uniqueness_of and combo of three fields

I have a model, Property, that has_many_polymorphs.  The associated join
table (labellings) has fields:
id (simple record id),
property_id,
labellable_id
labellable_type.

It''s basically the same system used with acts_as_taggable, except that
Property objects are a tree instead of a simple list (which doesn''t
have
any bearing on this problem, i think).

If i add a property to an object then a join table entry is created.  If
i add it again, i now have the object labelled twice with the same
property, which i don''t want.  I could say

object.properties << prop unless object.properties.include? prop

But that''s a bit cumbersome.

Ideally i''d use validates_uniqueness_of - i know that i can do this for
a combo of two values, with, eg

validates_uniqueness_of :property_id, :scope => :labellable_id

But i don''t know how to do it for three fields.  I tried this:

validates_uniqueness_of :property_id, :scope => [:labellable_id,
:labellable_type]

but got this exception when i tested it:
ActiveRecord::RecordInvalid: Validation failed: Property has already
been taken

Anyone know how to do this?

thanks
max
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Actually my syntax (validates_uniqueness_of :property_id, :scope =>
[:labellable_id, :labellable_type]) is correct, but i want it to simply
fail to save, rather than raise an exception.  Does anyone know how to
do this?
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Max Williams wrote:
> Actually my syntax (validates_uniqueness_of :property_id, :scope =>
> [:labellable_id, :labellable_type]) is correct, but i want it to simply
> fail to save, rather than raise an exception.  Does anyone know how to
> do this?
instead of model.save! or model.update!, use the form

if model.save
  # my model was saved successfully
else
  # my model didn''t save
end

also note

model.valid?

model.errors

hth

ilan


-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

> instead of model.save! or model.update!, use the form
> 
> if model.save
>   # my model was saved successfully
> else
>   # my model didn''t save
> end
Thanks Ilan - i played around with this a bit more and narrowed my 
problem down a bit.  It''s actually only the << (push) operator
that
breaks horribly - save just quietly fails, which is what i want.  So, as 
a way of adding a label (join table entry) to an object (eg of class 
Lesson) this works fine (ie fails without raising):

Label.create(:property_id => @prop.id, :labellable_id => @object.id, 
:labellable_type => @object.class.to_s)

However, it''s a bit clunky.  I''d rather just write

@prop.lessons << @object

But this *does* raise when it fails, ie if the join table entry exists 
already.

I can sort of get around it by doing

@prop.lessons << @object rescue false

but it would be nice to not have to do that.  I guess my problem is just 
with the << method.  Any ideas?

thanks
max

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---