all! I want to create additional has_many relation to select only needed columns
Example
class Price < ActiveRecord::Base
self.table_name = "pricelist_prices"
has_many :order_items, :primary_key=> :city_id, :foreign_key=> :city_id
has_many :orders, :through => :order_items
end
so it works now. But I would like to create association which works like :orders, but have :select option
Example
has_many :orders, :through => :order_items, :select=>"price"
But I don't want to override current :orders accociation. How to do this?
UPD Azoto show example with source option! It's ok, but when I use this accotiation in includes , it doesn't work.
Price.where(:id=>[12759,12758]).includes(:prices_from_orders)
(Object doesn't support #inspect)
Price.where(:id=>[12759,12758]).includes(:prices_from_orders).first
NoMethodError: undefined method `each' for nil:NilClass
from /Users/igorfedoronchuk/.rvm/gems/ruby-1.9.2-p180@new/gems/activerecord-3.2.1/lib/active_record/associations/preloader/association.rb:88:in `block in associated_records_by_owner'
UPD2
I realized problem, if you want to use such assotioation in includes method, also add primary_key selection, otherway AR don't know who is an owner of record.
has_many :orders, :through => :order_items, :select=>"id, price"
You can create a new relation
that does select
price.
has_many :price_of_orders, :through => :order_items,
:source => orders,
:select => :price
OR
How about an association extension?.
has_many :orders, :through => :order_items do
def just_price
select(:price)
end
end
Then you could do something like @price.orders.just_price