Should I move a parameter check from my controller to my model?

Question

I have a belongs_to relationship that can be removed without destroying either the parent or the child (transfer_form). Users can eliminate the parent relationship by selecting the blank option in a select dropdown while editing. Unfortunately, when they do this, I end up with

NoMethodError: undefined method `id' for "":String

Unless I perform a check on my parameters.

The following works but smells bad. Is it possible to move my current_school check to my model? Is this something I should do or should I leave it in my controller?

def update
  @transfer_form = TransferForm.find(params[:id])

  t = params[:transfer_form]
  if t['current_school'] == ""
    t['current_school'] = nil
  end

  respond_to do |format|
    if @transfer_form.update_attributes(t)
  ...
  end
end

Answer 1

You could always just do

params['current_school'] = nil if params['current_school'].blank?

but in reality the best practice would be to validate it in your model and do something like:

validates :current_school, :allow_blank => false

Then when you save it with an empty string it will error out, but I'm guessing you just want to set it to nil.

Update
I think its fine in your controller, but if you really want it in your model I would just use a before_save callback, that way you don't have any code in your controller, it will just automatically set every empty string to nil:

(untested)

before_save :sanitize_school

def sanitize_school
  current_school = nil if current_school.blank? 
end