prevent_destroy_if_any

This plugin adds ActiveRecord models a way to prevent destroy if specified has_many, has_one and/or belongs_to associations are present. This is achieved by adding a before_destroy callback that aborts the destroy and adds a base error on the instance when detecting associations.

It's inspired from this stackoverflow answer and was created to factorize this solution when you need it for various models in an application.

It has been tested with ActiveRecord 3 and 4, with Ruby 1.9 and 2+.

Add this line to your application’s Gemfile:

gem 'prevent_destroy_if_any'

A Person model for which you want to prevent destroy when it has an associated user, projects or public profile. Destroy will work if it has associated logs.

class Person < ActiveRecord::Base
  belongs_to :user
  has_many   :projects
  has_one    :public_profile
  has_many   :logs

  prevent_destroy_if_any :user, :projects, :public_profile
end

Then in Rails you can write your PeopleController destroy action like this:

def destroy
  person = Person.find params[:id]
  if person.destroy
    redirect_to people_url, notice: "Person successfully deleted"
  else
    redirect_to person, alert: person.errors.full_messages.join
  end
end

You can change the default base error message by setting the following key in your locale file(s):

en:
  prevent_destroy_if_any:
    messages:
      cannot_delete_parent_object: "Hey!!! You cannot delete %{parent_object} while %{associated_objects} exist"

Copyright © 2013 Florent Guilleux, released under the MIT license.