So, the first Rails project I ever worked on was in DataMapper. I loved it - but I never learned how to use migrations. People say DataMapper is so awesome because you don't need them most of the time (which is so true), but they usually fail to address the question "what about when you do need them?" For instance, when you need to alter a table, or remove a column, etc. Fortunately, there are people who have thought about, and solved, this problem for us, they just haven't had the time, apparently, to document the solution for us very well.
Installing dm-migrations was a piece of cake: just add gem 'dm-migrations'
to the Gemfile.
Using it, I ran into a few issues - partly as a result of my never having used ActiveRecord migrations in the first place, and partly because of a lack of conventions, or documentation for DataMapper migrations. So here are a few things I learned while trying to figur