Rails - Jul 2009 - Why!? A strange instance variable in action and view

I have a controller promos. When the edit action is called the
following error is given -
Called id for nil, which would mistakenly be 4 -- if you really wanted
the id of nil, use object_id

For simplicity the controller and view looks like this:

promos_controller.rb
--------------------------------
def edit
 @promo = Promo.find(params[:id])
end
------------------------------
edit.html.erb
-------------------------------
<%= @promo.id %>
----------------------------

However when I change the instance variable to say @home, or anything
else the view correctly displays the results.

Could anyone explain why it wouldn''t work for @promo?

On Thu, Jul 2, 2009 at 1:47 AM,
Dandan<icelavagles-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> I have a controller promos. When the edit action is called the
> following error is given -
> Called id for nil, which would mistakenly be 4 -- if you really wanted
> the id of nil, use object_id
>
> For simplicity the controller and view looks like this:
>
> promos_controller.rb
> --------------------------------
> def edit
>  @promo = Promo.find(params[:id])
> end
> ------------------------------
> edit.html.erb
> -------------------------------
> <%= @promo.id %>
> ----------------------------
>
> However when I change the instance variable to say @home, or anything
> else the view correctly displays the results.
>
> Could anyone explain why it wouldn''t work for @promo?
It''s not the instance variable name, it''s that that instance
variable
has a nil value.

What was the id parameter in the request?  I suspect that the find
failed to find a record with that id, which would cause it to return
nil.

Your controller should be doing something like:

def edit
   unless(@promo = Promo.find(params[:id]))
       # There was no promo with that id
       # Perform some appropriate error action
       # Which might involve setting the flash with an error msg
       # and redirecting somewhere
   end
end
-- 
Rick DeNatale

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Quoting Dandan <icelavagles-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:
[snip]
> promos_controller.rb
> --------------------------------
> def edit
>  @promo = Promo.find(params[:id])
> end
> ------------------------------
> edit.html.erb
> -------------------------------
> <%= @promo.id %>
> ----------------------------

I find that model.id is troublesome.  model[:id] works quite reliably for me.

HTH,
  Jeffrey