eager loading with has_many :through

rubyonrails-talk
1

I've got the following associations:

class Photo < AR::Base   has_many :slides   has_many :albums, :through => :slides

  # this has an attachment_fu attachment which creates a thumbnail image for each uploaded photo. end

class Album < AR::Base   has_many :slides   has_many :photos, :through => :slides end

class Slide < AR::Base   belongs_to :photo   belongs_to :album end

In my Photos#index action I render all thumbnails and list the albums that the photos belong to. I'm using attachment_fu, the parent image is the one with the slide and album association, the thumbnail image does not have that association.

The index action is hitting the database to load all albums that belong to a photo, how can I cut that down to one query for eager loading?

Currently I'm doing:

  Photo.find(:all, :include => :parent, :conditions ['thumbnail = ?', 'small'])

but I can't figure out how to eager-load the albums, through slides, based on the parent photo (since the thumbnail doesn't have any associated slides or albums.)

Thanks for any help,

Stu

2

Currently I'm doing:

Photo.find(:all, :include => :parent, :conditions ['thumbnail = ?', 'small'])

but I can't figure out how to eager-load the albums, through slides, based on the parent photo (since the thumbnail doesn't have any associated slides or albums.)

You can nest includes, eg Photo.find :all, :include => {:parent => [:some_association_on_parent, :another_association_on_parent]}

Fred

3

Sweet, thanks Fred.