Prevent deletion of records where a certain field is non-blank

Question

If I have a Widget model as follows:

create_table "widgets", id: :serial, force: :cascade do |t|
  t.string "name"
  t.integer "quantity"
end

... how do I prevent a destroy action if quantity is something other than nil or zero? I assume this is something I should do in the model rather than the controller?

Answer 1

I have figured it out:

class Widget < ApplicationRecord

  before_destroy :ensure_quantity_blank

protected

  def ensure_quantity_blank
    if !self.quantity.blank?
      errors.add(:quantity, "Cannot delete widget with a quantity")
      throw(:abort)
    end
  end

end

See also How do I 'validate' on destroy in rails