ActiveRecord.id does not work within named_scope block

Rails
1

Hi,

Trying to create a named_scope that would check that the record is not
itself.

I have companies and contacts, where a contact can be a primary
contact for a company:

class Company
has_many :contacts
end

class Contact < ActiveRecord::Base
belongs_to :company

named_scope :primary, :conditions => { :is_primary => true } do
def mark_as_non_primary!
each { |p| p.update_attribute(:is_primary, false) }
end
end

named_scope :but_not_itself, :conditions => [‘contacts.id != ?’,
id]
end

So I would like to do something like this from Contact model:

company.contacts.primary.but_not_itself.mark_as_non_primary!

However this does not work because id method within but_not_itself
named_scope returns an Object.id (instance id) and not ActiveRecord id
(database id).

How do I make it work?

Thanks!

2

On Aug 18, 11:21 pm, Swartz [email protected] wrote:

end
named_scope :but_not_itself, :conditions => [‘contacts.id != ?’,

The reason this does not work is because that expression “id” is
evaluated when named_scope is call to create the scope, ie when the
class is loaded, so self is the class Contact.
It’s the same reason why doing :conditions => [‘created_at < ?’,
1.day.ago] won’t work properly: the 1.day.ago is evaluated once, at
class load time and then never again.

Luckily instead of passing a hash of options you can pass a lambda
that returns a hash of options. Since that proc will be called when
the scope is loaded and in the right context you should be fine.

Fred

3

Hi Fred,

Thanks for your input.

So far I changed that named_scope into this:
named_scope :but_not_itself,
lambda { |id| { :conditions => [‘contacts.id != ?’, id]} }

Is that what you meant?

Is there a better way to do this?

Now I have to do this:
company.contacts.primary.but_not_itself(self.id).mark_as_non_primary!

seems, to me at least, kind of ugly having to pass self.id… :slight_smile:

By the way my inspiration for this came from
http://ryandaigle.com/articles/2008/3/24/what-s-new-in-edge-rails-has-finder-functionality
Where the author has User.inactive.activate to very neatly activate
inactive users.

–
Swartz

On Aug 18, 5:04 pm, Frederick C. [email protected]