module Mongoid
  module Factory
    extend self
    def from_db(klass, attributes = nil, selected_fields = nil)
      type = (attributes || {})[TYPE]
      if type.blank? || type =~ /http:\/\//
        klass.instantiate(attributes, selected_fields)
      else
        type.camelize.constantize.instantiate(attributes, selected_fields)
      end
    end
  end
end

{
    "_id" : "richtext",
    "ops" : [
        {
            "insert" : "Hi!"
        }
    ],
    "_type" : "http://sharejs.org/types/rich-text/v1",
    "_v" : 1,
    "_m" : {
        "ctime" : 1476286743185.0,
        "mtime" : 1476286743185.0
    },
    "_o" : ObjectId("57fe591743247f0011b3e04d")
}

Running via Spring preloader in process 16
Loading development environment (Rails 5.0.0)
irb(main):001:0> RealtimePage.first
Overwriting existing field _id in class RealtimePage.
MONGODB | Adding mongo:27017 to the cluster.
MONGODB | mongo:27017 | furrow_development.find | STARTED | {"find"=>"realtime_pages", "filter"=>{}, "sort"=>{"_id"=>1}, "limit"=>1, "singleBatch"=>true}
MONGODB | mongo:27017 | furrow_development.find | SUCCEEDED | 0.000988278s
NameError: wrong constant name
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/inflector/methods.rb:270:in `const_get'
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/inflector/methods.rb:270:in `block in constantize'
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/inflector/methods.rb:266:in `each'
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/inflector/methods.rb:266:in `inject'
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/inflector/methods.rb:266:in `constantize'
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/core_ext/string/inflections.rb:66:in `constantize'
    from /bundler-cache/gems/mongoid-6.0.0/lib/mongoid/factory.rb:46:in `from_db'
    from /bundler-cache/gems/mongoid-6.0.0/lib/mongoid/relations/eager.rb:16:in `with_eager_loading'
    from /bundler-cache/gems/mongoid-6.0.0/lib/mongoid/contextual/mongo.rb:248:in `block in first'
    from /bundler-cache/gems/mongoid-6.0.0/lib/mongoid/contextual/mongo.rb:501:in `try_cache'
    from /bundler-cache/gems/mongoid-6.0.0/lib/mongoid/contextual/mongo.rb:246:in `first'
    from /bundler-cache/gems/mongoid-6.0.0/lib/mongoid/contextual.rb:20:in `first'
    from /bundler-cache/gems/mongoid-6.0.0/lib/mongoid/findable.rb:148:in `first'
    from (irb):1
    from /bundler-cache/gems/railties-5.0.0/lib/rails/commands/console.rb:65:in `start'
    from /bundler-cache/gems/railties-5.0.0/lib/rails/commands/console_helper.rb:9:in `start'
... 8 levels...
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/dependencies.rb:287:in `load'
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/dependencies.rb:287:in `block in load'
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/dependencies.rb:259:in `load_dependency'
    from /bundler-cache/gems/activesupport-5.0.0/lib/active_support/dependencies.rb:287:in `load'
    from /bundler-cache/gems/spring-1.7.2/lib/spring/commands/rails.rb:6:in `call'
    from /bundler-cache/gems/spring-1.7.2/lib/spring/command_wrapper.rb:38:in `call'
    from /bundler-cache/gems/spring-1.7.2/lib/spring/application.rb:191:in `block in serve'
    from /bundler-cache/gems/spring-1.7.2/lib/spring/application.rb:161:in `fork'
    from /bundler-cache/gems/spring-1.7.2/lib/spring/application.rb:161:in `serve'
    from /bundler-cache/gems/spring-1.7.2/lib/spring/application.rb:131:in `block in run'
    from /bundler-cache/gems/spring-1.7.2/lib/spring/application.rb:125:in `loop'
    from /bundler-cache/gems/spring-1.7.2/lib/spring/application.rb:125:in `run'
    from /bundler-cache/gems/spring-1.7.2/lib/spring/application/boot.rb:19:in `<top (required)>'
    from /usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from -e:1:in `<main>'
irb(main):002:0>