Thank God for Lighthouse.

I got this error (private method `split' called for :id:Symbol, in my case) because my has_many statement had :order => :id specified (yes, it looks a trivial order; it's legacy code, so give me a break).

Aha! We shouldn't be using symbols to represent table columns in our has_many statements. We're really talking about an SQL fragment, anyway, so it seems more sensible to use a string anyway. Consider a case where you want to include another table:

class Organization < ActiveRecord::Base
  has_many :users, :order => "accounts.number", :include => :account
end

class User < ActiveRecord::Base
  belongs_to :organization
  belongs_to :account
end

class Account < ActiveRecord::Base
  has_one :user
end

Certainly there's no way to do :accounts.number or something like that, and it doesn't make sense anyway. Long story short, it's OK to use Symbols for table names, but leave the columns to the strings, please!