Why!? A strange instance variable in action and view

Rails
1

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?

2

On Thu, Jul 2, 2009 at 1:47 AM, Dandan[email protected] wrote:

def edit

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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3

Quoting D. [email protected]:
[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