add_column for references (Rails)

Question

While it’s too late to get any points out of this, I thought I’d post the best way for posterity 🙂

use change_table instead of create_table to add columns to a table that already exists, with all the TableDefinition goodness:

self.up do
  change_table :comments do |t|
    t.references :author
  end
end

This might seem trivial, but other gems like Devise make heavy use of their own custom table definitions, and this way you can still use them.