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Rails Plugin for DataMapper


This is a legacy gem, that provides rails 2.x support for DataMapper. Those looking to use DataMapper with Rails3 should use dm-rails which can be found at


add the following line to your projects environment.rb

config.gem “rails_datamapper”


This will install the datamapper rake tasks:

script/generate dm_install

Three generators are added by default

script/generate dm_model script/generate rspec_dm_model script/generate dm_migration

The first two add a migration but you can call

script/generate dm_model –skip-migration script/generate rspec_dm_model –skip-migration

To avoid any dependency on active record add this to your projects environment.rb

config.frameworks -= [ :active_record ]

Session Store

Change config/initializers/session_store.rb to something like the following:

ActionController::Base.session_store = :data_mapper_store ActionController::Base.session = {

:expires_after => 7.days,
:key           => '_session_id',


Then create the sessions table with: rake db:sessions:create

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