ActiveRecord and the DRY3 principle

ActiveRecord is a beautiful piece of software. But just step aside of the prescribed road, and you are guaranteed to have problems.

This time, my problems began when I started to design the model first. I quickly laid out a couple of screens of objects, wrote the connection line and ran the code.

class SubjectLocator  "String"

# a dozen more objects follow...

  :adapter  => "mysql",
  :host     => "localhost",
  :username => "test",
  :password => "test",
  :database => "activerecord"

It has not come as a surprise that ruby replied with an exception.

Table 'activerecord.subject_locator' doesn't exist: SHOW FIELDS FROM `subject_locator` (ActiveRecord::StatementInvalid)

What surprised me is that after half an hour of search on the internet, I found no way to boostrap a DB schema out of the model. There were discussions on the rails mailing list. They even went as far as suggesting non-destructive automatic migrations, a feature that exists in Hibernate for at least 5 years already. None dared to implement either.

I am now left with one solution. Apply the DRY3 principle, aka "Do Repeat Yourself 3.times" and start writing the migrations script for my models (repeat!), as well as an SQL schema for my MySQL database that would keep indexes, views and triggers in addition to what I will boostrap from migrations (repeat again!)