How do I 'validate' on destroy in rails

Question

On destruction of a restful resource, I want to guarantee a few things before I allow a destroy operation to continue? Basically, I want the ability to stop the destroy oper

Answer 1

State of affairs as of Rails 6:

This works:

before_destroy :ensure_something, prepend: true do
  throw(:abort) if errors.present?
end

private

def ensure_something
  errors.add(:field, "This isn't a good idea..") if something_bad
end

validate :validate_test, on: :destroy doesn't work: https://github.com/rails/rails/issues/32376

Since Rails 5 throw(:abort) is required to cancel execution: https://makandracards.com/makandra/20301-cancelling-the-activerecord-callback-chain

prepend: true is required so that dependent: :destroy doesn't run before the validations are executed: https://github.com/rails/rails/issues/3458

You can fish this together from other answers and comments, but I found none of them to be complete.

As a sidenote, many used a has_many relation as an example where they want to make sure not to delete any records if it would create orphaned records. This can be solved much more easily:

has_many :entities, dependent: :restrict_with_error