Caius Theory

Now with even more cowbell…

Use datamapper sessions with merb & datamapper


Can’t use merb sessions with datamapper & mysql, get back an error about needing an id on the text column or something (I had the error a couple of days ago.)


I suggest grabbing merb_datamapper svn source to fix this in. To do so make sure you have subversion installed on your machine (I’m assuming a Unix based machine here.)

  1. Checkout the source

     svn co
  2. Open up the affected file in your favourite editor (I use TextMate)

     cd merb_datamapper
     mate lib/merb/sessions/data_mapper_session.rb
  3. Find line 25 that contains

     `property :session_id, :text, :lazy => false, :key => true`

    and remove :text, :lazy => false to replace it with :string

     `property :session_id, :string, :key => true`

    Save and close the file, thats the editing done. Now to install the gem.

  4. Build the gem

     rake gem
  5. Install the gem

     sudo gem install pkg/merb_datamapper-0.5.gem

And you’re away with the fix installed. Now just run merb to create your sessions table in the db. Hope this helped!