Check for loaded sql object in Rails - ruby-on-rails

Question

My model:
class User
has_many :items
end
class Item
belongs_to :user
def self.with_color(color, is_loaded)
if is_loaded
self.select { |i| i.color == color }
else
self.where(:color => color)
end
end
end
There are 2 types of code in my controllers.
## this line loads 'items' of the user and selects with the red color ##
#colored_items = current_user.items.with_color('red', false)
## this code should not load items twice ##
#user_with_items = User.includes(:items).find(params[:user_id])
(...)
colored_items = #user_with_items.with_color('red', true)
If I only write "select" version, it doesnt work with 1 example, and 'where' version loads items again even if they are already loaded.
How can I check is object already loaded or not?

Answer 1

How about using scopes?
Taken from example:
class Shirt < ActiveRecord::Base
scope :colored, lambda { |color| where(:color => color) }
end
More to read here: http://apidock.com/rails/ActiveRecord/Scoping/Named/ClassMethods/scope
With your example, this should be (not tested)
class User
has_many :items
end
class Item
belongs_to :user
scope :colored, lambda { |color| where(:color => color) }
end
## this line loads 'items' of the user and selects with the red color ##
#colored_items = current_user.items.colored('red')
## use of 'includes' here to solve (n+1) issue
#user_with_items = User.includes(:items).find(params[:user_id])
colored_items = #user_with_items.colored('red')
Update:
class User < ActiveRecord::Base
has_many :items
def colored_items(color)
self.items.to_a.select { |i| i.color == color }
end
end
user = User.includes(:items).find(1)
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 1]]
Item Load (0.4ms) SELECT "items".* FROM "items" WHERE "items"."user_id" IN (1)
=> #<User id: 1, name: nil, created_at: "2012-03-25 00:39:52", updated_at: "2012-03-25 00:39:52">
user.colored_items "red"
=> [#<Item id: 1, color: "red", user_id: 1, created_at: "2012-03-25 00:41:00", updated_at: "2012-03-25 00:41:00">]
user.colored_items "blue"
=> [#<Item id: 2, color: "blue", user_id: 1, created_at: "2012-03-25 00:41:04", updated_at: "2012-03-25 00:41:04">]
So only 2 SQLs here.