Rails: ActiveResource - Can I set the ID explicitly?

Question

I am using ActiveResource in Rails to manage entities in a separate database over REST.

I have been trying to explicitly manage the IDs of the remote resources, as for the current case it is simplest to just re-use the local resource's ID, rather than maintain a different field.

Unfortunately I have not been able to get this working as the code for new? in ActiveResource::Base is

  def new?
    id.nil?
  end

and save is

 def save
   new? ? create : update
 end

So from that by definition it is impossible to set an ID of a resource and save it as a new resource.

create and update are protected methods, so if I hacked the ActiveResource::Base code perhaps that would make it work, but I am loath to do that.

Is there a correct way of doing this? Or is what I am trying to do just bad, and I shouldn't do it?

Answer 1

You're working against the intentions of ActiveResource. ActiveResource provides an interface to REST webservices, which by convention return the assigned ID when you do a create.

That said, if you control the resource you're using, and you have modified its behavior to take an ID when saving a new record, you could modify ActiveResource::Base to conform. It's really not uncommon for folks in Rails to make additions and changes to base classes; you just put your patch in lib and include it somewhere in your startup stuff.

I don't think it's a good idea, necessarily, but it is possible. :)

Answer 2

In new rails (tested 2.3.2) id can be set, as saving logic has changed a bit (now records have boolean field @newrecord to eliminate that id.nil?).

record = Model.new
record.id = 123
record.save!