How to use mongo_mapper with rails 4?

Question

I am trying to use rails 4.0.0 with mongo_mapper 0.12.0 and getting that message

Bundler could not find compatible versions for gem "activesupport":
  In Gemfile:
    mongo_mapper (~> 0.12.0) ruby depends on
      activesupport (~> 3.0) ruby

    rails (= 4.0.0) ruby depends on
      activesupport (4.0.0)

Rails 4 and mongo_mapper is still not compatible?

Answer 1

Mongomapper 0.12.0 doesn't work with activesupport 4.0.0

You can check it on the file mongo_mapper.gemspec:

s.add_dependency 'activemodel',   '~> 3.0'

But you can use version 0.13.0.beta2, if you check the file mongo_mapper.gemspec for it:

s.add_dependency 'activesupport', '>= 3.0'

So all you have to do in your Gemfile

gem 'mongo_mapper', '>= 0.13.0.beta2'