STI joins

Rails
1

I have 2 models set up using single table inheritance (STI) with
belongs_to relationships to a third model.

class CoveredEntity < Entity
belongs_to :breach
…
end

class BusinessAssociate < Entity
belongs_to :breach
…
end

class Breach < ActiveRecord::Base
has_one :covered_entity
has_one :business_associate
end

In my index view for breaches controller I am displaying the
covered_entity.name and the business_associate.name (if it exists). I
want to allow the users to sort the index table by either of these
values; however, since they use STI and are the same table, just doing
@breaches.includes(:covered_entity).includes(:business_associate).order("#{sort_column}
#{sort_direction}") does not work.

I can get around this by using .joins("inner join (select * from
entities where entities.type = ‘CoveredEntity’) as covered_entities left
join (select * from entities where entities.type = ‘BusinessAssociate’)
as business_associates) and then I am able to use
.order(“business_associate.name”) or .order(“covered_entities.name”) and
get the desired results.

I was curious if there is another way to do this that would not require
me to write out the joins by hand ( passing an alias to association or
includes for example).

2

On Friday, July 22, 2011 7:12:07 AM UTC-6, Juan Alvarado wrote:

belongs_to :breach
covered_entity.name and the business_associate.name (if it exists). I
desired results.

I was curious if there is another way to do this that would not require me
to write out the joins by hand ( passing an alias to association or includes
for example).

Any reason why you can’t use something like this?

sort_by_name_of = use_business_entity ? :business_associate :
:covered_entity
@breaches = @breaches.joins(sort_by_name_of).order(:name) if
sort_by_name

works in my quick, test rails 3.0.7 app

Is using #joins abhorrent to you?

Also, as an aside, any reason you don’t/can’t put your “belongs_to
:breach”
relationship in your Entity class (since both STI sub-types both have
the
relationship of the same name)?