I recently had to scratch my head over a strange exception message I'd never seen before:
undefined method `render' for #<SomeTemplate:0xb17da594>
The problem was, it came with *no* application trace at all... just the usual Rails stack-trace.
I had to guess at where the problem came from by grepping for SomeTemplate in the controller-action that had exploded, and came across the following line of code:
@template = SomeTemplate.new(params[:some_template])
Now SomeTemplate is a model of ours, and prior to this error occurring that line of code had been:
@temp = SomeTemplate.new(params[:some_template])
I have a strong aversion to calling any variable "temp", because my reaction to seeing a variable called temp is to say "a temporary what?" not "oh, that's an instance of a template", and if I'm getting the wrong idea when I look at a variable name - that's an indication it should be changed.
So I renamed it...
Unfortunately, it turns out that @template is a magic variable in Rails that refers to the template to be rendered in a given controller action.
So Just Don't Do That.
The code has now been rewritten to the following, and works just fine:
@some_template = SomeTemplate.new(params[:some_template])