affected_on_destroy

affected_on_destroy is a simple Rails plugin that recursively reflects on defined associations and lets you know which records will be deleted/nullified when using :dependent => :destroy or :dependent => :nullify.

Installation

config.gem 'murbanski-affected_on_destroy', :lib => 'affected_on_destroy', :source => 'http://gems.github.com'

Usage

schema.rb:

create_table "users", :force => true do |t|
  t.string   "login"
  t.string   "password"
  t.datetime "created_at"
  t.datetime "updated_at"
end

create_table "blogs", :force => true do |t|
  t.integer  "user_id"
  t.string   "name"
  t.datetime "created_at"
  t.datetime "updated_at"
end

create_table "posts", :force => true do |t|
  t.integer  "blog_id"
  t.text     "content"
  t.datetime "created_at"
  t.datetime "updated_at"
end

models:

class User < ActiveRecord::Base
  has_many :blogs, :dependent => :destroy
end

class Blog < ActiveRecord::Base
  belongs_to :user
  has_many :posts, :dependent => :nullify
end

class Post < ActiveRecord::Base
  belongs_to :blog
end

Sample script/console session:

>>  marcin = User.create(:login => 'marcin', :password => 'my_pass')
=> #<User id: 1, login: "marcin", password: "my_pass", created_at: "2009-06-26 01:47:36", updated_at: "2009-06-26 01:47:36">

>> blog = marcin.blogs.create(:name => 'My Ruby Blog')
=> #<Blog id: 1, user_id: 1, name: "My Ruby Blog", created_at: "2009-06-26 01:47:57", updated_at: "2009-06-26 01:47:57">

>> blog.posts.create(:content => 'Ruby tricks #1')
=> #<Post id: 1, blog_id: 1, content: "Ruby tricks #1", created_at: "2009-06-26 01:48:40", updated_at: "2009-06-26 01:48:40">
>> blog.posts.create(:content => 'Ruby tricks #2')
=> #<Post id: 2, blog_id: 1, content: "Ruby tricks #2", created_at: "2009-06-26 01:48:45", updated_at: "2009-06-26 01:48:45">

What records will be affected when we destroy user 'marcin'?

>> marcin.affected_on_destroy
=> [#<Blog id: 1, user_id: 1, name: "My Ruby Blog", created_at: "2009-06-26 01:47:57", updated_at: "2009-06-26 01:47:57">, 
#<Post id: 1, blog_id: 1, content: "Ruby tricks #1", created_at: "2009-06-26 01:48:40", updated_at: "2009-06-26 01:48:40">, 
#<Post id: 2, blog_id: 1, content: "Ruby tricks #2", created_at: "2009-06-26 01:48:45", updated_at: "2009-06-26 01:48:45">]

Which models are affected when destroying user?

>> User.affected_on_destroy
=> ["Blog", "Post"]

Same for blog:

>> Blog.affected_on_destroy
=> ["Post"]

Rails Version

Works on Rails 2.3 and 2.2