# Dynamically add includes to an association? **URL:** \ **Category:** Rails\ **Created:** [January 22, 2009, 11:38am UTC](https://www.ruby-forum.com/t/dynamically-add-includes-to-an-association/158349 "2009-01-22T11:38:05Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [January 22, 2009, 11:38am UTC](https://www.ruby-forum.com/t/dynamically-add-includes-to-an-association/158349/1 "2009-01-22T11:38:05Z")
I have an association user.lessons. Sometimes i just want the lessons, other times i want the lessons to eager-load one of their own associations, ‘assets’. Theres a couple of ways i can see to deal with this and i’m not super happy with any of them. approach 1) Make two associations: has\_many :lessons has\_many :lessons\_with\_assets, :class\_name =\> “Lesson”, :include =\> [:assets] #then, if i want the assets, call @user.lessons\_with\_assets This is actually my favorite but it still feels a bit clumsy approach 2) Don’t use the association if i want to eager load #just do a regular find Lesson.find\_all\_by\_user\_id(@user.id, :include =\> [:assets]) Is there another way? This example is simple but i have other associations that go through join tables and are polymorphic (eg using the has\_favorite plugin) that are a bit more arsey to use. thanks max ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [January 22, 2009, 12:09pm UTC](https://www.ruby-forum.com/t/dynamically-add-includes-to-an-association/158349/2 "2009-01-22T12:09:18Z")
On Thu, Jan 22, 2009 at 12:38 PM, Max W. \< removed\_email\_address@domain.invalid\> wrote: > associations that go through join tables and are polymorphic (eg using > the has\_favorite plugin) that are a bit more arsey to use. > > ## thanks max > > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). > > > Max There’s another way, named\_scopes. in the Lesson model, add named\_scope :with\_assets, :include =\> :assets then you can call lessons or lessons.with\_assets – Andrew T. [http://ramblingsonrails.com](http://ramblingsonrails.com) [http://www.linkedin.com/in/andrewtimberlake](http://www.linkedin.com/in/andrewtimberlake) “I have never let my schooling interfere with my education” - Mark Twain ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [January 22, 2009, 12:37pm UTC](https://www.ruby-forum.com/t/dynamically-add-includes-to-an-association/158349/3 "2009-01-22T12:37:17Z")
aha…so, if i have lots of different associations (in user and other classes) that return a collection of lessons i can just add “.with\_assets” to the end? eg user.usb\_lessons.with\_assets user.lessons.with\_assets resource.recent\_lessons.with\_assets etc ? ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [January 22, 2009, 12:58pm UTC](https://www.ruby-forum.com/t/dynamically-add-includes-to-an-association/158349/4 "2009-01-22T12:58:23Z")
After a bit of experimentation i confirmed for myself that that is indeed the case 🙂 thanks a lot Andrew, this is great. I’d seen named scopes before but never really used them much and never realised their potential for managing includes. One thing i noticed which is interesting…lessons are joined to assets through a join table, ‘elements’. if i use the with\_assets scope for an association that goes through a join table, then rails does a further join to the assets table, like you’d expect with an include, so we have this situation: user JOIN user\_usb\_lessons JOIN lessons JOIN elements JOIN assets If, however, it’s a simple association (such as user.lessons, which just uses Lesson’s user\_id field) then rails splits it off into three sql calls: the first to load the lessons, the second to load the elements (join table records) and the third to load the assets. I guess that three seperate simple calls were seen as preferable to a single JOIN? Anyway, thanks again! max ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [January 22, 2009, 1:04pm UTC](https://www.ruby-forum.com/t/dynamically-add-includes-to-an-association/158349/5 "2009-01-22T13:04:47Z")
On Thu, Jan 22, 2009 at 1:58 PM, Max W. \< removed\_email\_address@domain.invalid\> wrote: > I guess that three seperate simple calls were seen as preferable to a > single JOIN? > > ## Anyway, thanks again! max > > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). > > > Yes, on more complicated joins, where Rails thinks it will be better, it does split the query into multiple queries. – Andrew T. [http://ramblingsonrails.com](http://ramblingsonrails.com) [http://www.linkedin.com/in/andrewtimberlake](http://www.linkedin.com/in/andrewtimberlake) “I have never let my schooling interfere with my education” - Mark Twain ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [January 22, 2009, 12:58pm UTC](https://www.ruby-forum.com/t/dynamically-add-includes-to-an-association/158349/6 "2009-01-22T12:58:48Z")
On 22 Jan 2009, at 11:08, Andrew T. wrote: > then you can call > lessons > or > lessons.with\_assets See also [http://ryandaigle.com/articles/2008/8/20/named-scope-it-s-not-just-for-conditions-ya-know](http://ryandaigle.com/articles/2008/8/20/named-scope-it-s-not-just-for-conditions-ya-know) Fred