ActiveRecord: How can I clone nested associations? - ruby-on-rails

Question

I'm currently cloning a single-level association like this:
class Survey < ActiveRecord::Base
def duplicate
new_template = self.clone
new_template.questions << self.questions.collect { |question| question.clone }
new_template.save
end
end
So that clones the Survey then clones the Questions associated with that survey. Fine. That works quite well.
But what I'm having trouble with is that each question has_many Answers. So Survey has_many Questions which has_many Answers.
I can't figure out how to clone the answers properly. I've tried this:
def duplicate
new_template = self.clone
self.questions.each do |question|
new_question = question.clone
new_question.save
question.answers.each do |answer|
new_answer = answer.clone
new_answer.save
new_question.answers << answer
end
new_template.questions << question
end
new_template.save
end
But that does some weird stuff with actually replacing the original answers then creating new ones, so ID's stop matching correctly.

Answer 1

Use deep_clonable gem
new_survey = original_survey.clone :include => [:questions => :answers]

Answer 2

You may also like the Amoeba gem for ActiveRecord 3.2.
In your case, you probably want to make use of the nullify, regex or prefix options available in the configuration DSL.
It supports easy and automatic recursive duplication of has_one, has_many and has_and_belongs_to_many associations, field preprocessing and a highly flexible and powerful configuration DSL that can be applied both to the model and on the fly.
be sure to check out the Amoeba Documentation but usage is pretty easy...
just
gem install amoeba
or add
gem 'amoeba'
to your Gemfile
then add the amoeba block to your model and run the dup method as usual
class Post < ActiveRecord::Base
has_many :comments
has_and_belongs_to_many :tags
amoeba do
enable
end
end
class Comment < ActiveRecord::Base
belongs_to :post
end
class Tag < ActiveRecord::Base
has_and_belongs_to_many :posts
end
class PostsController < ActionController
def some_method
my_post = Post.find(params[:id])
new_post = my_post.dup
new_post.save
end
end
You can also control which fields get copied in numerous ways, but for example, if you wanted to prevent comments from being duplicated but you wanted to maintain the same tags, you could do something like this:
class Post < ActiveRecord::Base
has_many :comments
has_and_belongs_to_many :tags
amoeba do
exclude_field :comments
end
end
You can also preprocess fields to help indicate uniqueness with both prefixes and suffixes as well as regexes. In addition, there are also numerous options so you can write in the most readable style for your purpose:
class Post < ActiveRecord::Base
has_many :comments
has_and_belongs_to_many :tags
amoeba do
include_field :tags
prepend :title => "Copy of "
append :contents => " (copied version)"
regex :contents => {:replace => /dog/, :with => "cat"}
end
end
Recursive copying of associations is easy, just enable amoeba on child models as well
class Post < ActiveRecord::Base
has_many :comments
amoeba do
enable
end
end
class Comment < ActiveRecord::Base
belongs_to :post
has_many :ratings
amoeba do
enable
end
end
class Rating < ActiveRecord::Base
belongs_to :comment
end
The configuration DSL has yet more options, so be sure to check out the documentation.
Enjoy! :)

Answer 3

Without using gems, you can do the following:
class Survey < ApplicationRecord
has_and_belongs_to_many :questions
def copy_from(last_survey)
last_survery.questions.each do |question|
new_question = question.dup
new_question.save
questions << new_question
end
save
end
…
end
Then you can call:
new_survey = Survey.create
new_survey.copy_from(past_survey)
That will duplicate all questions from last Survey to new Survey and tie them.

Answer 4

Shouldn't it be..
new_question.answers << new_answer
end
new_template.questions << new_question

Answer 5

You can also alias the rails dup method, as follows:
class Survey
has_many :questions, :inverse_of=>:survey, :autosave=>true
alias orig_dup dup
def dup
copy=orig_dup
copy.questions=questions
copy
end
end
class Questions
belongs_to :survey, :inverse_of=>:questions
has_many :answers, :inverse_of=>:question, :autosave=>true
alias orig_dup dup
def dup
copy=orig_dup
copy.answers=answers
copy
end
end
class Answer
belongs_to :question
end
and then you can do this
aaa = Survey.find(123).dup
aaa.save