Question

Can I sort a list of objects by a property of an associated object?

For example with the following class

class RosterSlot < ActiveRecord::Base
  belongs_to :event
  belongs_to :skill
  belongs_to :person
end

I want to do something like
RosterSlot.find(:all, :order => skill.name)

which means activerecord needs to do a join and order.

Any ideas?

Answer 1

Yes, you can use the :include option to do the join.

RosterSlot.find(:all, :include => [:skill], :order => "skills.name ASC")

The :order option takes a SQL fragment, so skills is a reference to the plural database table name.

The :include takes an array of Active Record Associations.

See http://www.railsbrain.com/api/rails-2.3.2/doc/index.html?a=M002313&name=find for more info.