uninitialized constant Moped::BSON in rails 4 app on heroku

Question

I just updated from rails 3 to rails 4. Everything works locally, but deployed on heroku, I get the following error:

ActionView::Template::Error (uninitialized c         


        

Answer 1

The following worked for me:

add to Gemfile:

gem "bson"
gem "moped", github: "mongoid/moped"

bundle install

add to application.rb:

require "bson"
require "moped"
Moped::BSON = BSON

Answer from: https://github.com/mongoid/mongoid/issues/3455

Answer 2

See this comment from Moped's author as of Moped 2.0.0 (which is the version , as of this writing, used as the driver in mongoid 4.0.0):

Moped's BSON implementation has been removed in favor of the 10gen bson gem 2.0 and higher. All Moped::BSON references should be changed to just BSON.

https://github.com/mongoid/moped/blob/master/CHANGELOG.md

Answer 3

This error can also be caused by having references to Moped::BSON in serialized cookies/session. Deleting cookies fixes it then.