DejaVue

Yet another gem to store versions of your model’s data, but using MongoDB as backend. Based on PaperTrail (github.com/airblade/paper_trail/).

It also allows you to versionate associated models (by now, only one-to-one associations).

Dependencies

It depend on mongo and mongo_mapper gems. Your MongoDB connection might already have been created.

As it uses a NoSQL db, you don’t need migrations to start using it.

Why choose DejaVue

The main goal of DejaVue is to keep track of associated models. It’s useful for a model whose relations change among time and to see how it really looked like at a certain point.

As in PaperTrail, there are 3 kinds of versions: create, update and destroy

Installing

$ bundle install

$ gem install gemcutter

$ gem build deja_vue.gemspec
$ gem install ./deja_vue-*.gem

Beggining with DejaVue: Add to your model

Add a single line and your model will start beeing versionated:

def SomeModel < ActiveRecord::Base
 has_deja_vue
end

Or, for example, use the ignore option:

def SomeModel < ActiveRecord::Base
 has_deja_vue :ignore => :location
end

Configuring user dynamically

Sometimes you might need to set the user that is changing the model data dynamically, eg. while processing background jobs.

In such case, you can set user using:

DejaVue.setting_user_as('admin') do
 @post.title = 'new title'
 @post.save
end

This way you will set who_did_it as ‘admin’, create a new history version and then rollback to previous user.

More Options

You might pass some options, including:
:ignore                 | An Array of fields that will be ignored. If
                        | only those fields have changed, then no version
                        | will be created.
                        | has_deja_vue :ignore => :last_exported_on
:associations           | Store associated models to be record with the model
                        | so it can be fully restored. Right now it works only
                        | with has_one / belongs_to relationships.
                        | Ex.:
                        | class Account < ActiveRecord::Base
                        |   has_one :account_preference
                        |
                        |   has_deja_vue :associations => [:account_preference]
                        | end
                        |
:extra_info_fields      | Almost the same as the above option. But it handles
                        | more simple info (like strings, integers, floats).
                        | Useful to store a tag_list field or a counter cache
                        | Ex:
                        |
                        | class BlogPost < ActiveRecord::Base
                        |   acts_as_taggable_on :tags
                        |
                        |   has_deja_vue :extra_info_fields => [:tag_list]
                        | end
                        |
:who_did_it             | a default value for record who_did_it when you
                        | are not in a request-response cycle (ex. in a job).
                        | Ex.:
                        | has_deja_vue :who_did_it => 'admin'
                        | Alternatively you are able to set the user right
                        | before save the model that will be versionated, using:
                        | DejaVue.who_did_it = 'otavio'
                        | SomeModel.save

Important info regarding DejaVue behaviour

Differently from PaperTrail, each version will record the current model info.

So PapelTrail create version have reify == nil

DejaVue have create version == model_data_while_creating

Reporting Bugs

github.com/riopro/deja_vue/issues

Authors

Otávio Sampaio (osampaio at riopro dot com dot br)

Rodrigo Oliveira (roliveira at riopro dot com dot br)