Proper usage of .includes and .joins - ruby-on-rails

Question

I have 3 models
Options:
class Option < ActiveRecord::Base
attr_accessible :key, :name
belongs_to :item_options
end
ItemOptions
class ItemOption < ActiveRecord::Base
# attr_accessible :title, :body
belongs_to :item
belongs_to :option
end
and Item:
class Item < ActiveRecord::Base
has_many :item_options
has_many :options, :through => :item_options
end
And I need my controller to return all items with their options in JSON format so i'm trying to use .includes but with no luck:
items = Item
.order('id')
.where(manufacturer)
.where('is_active')
render :json => {:data => items.offset(offset), :total => items.count}.to_json(
:include => :options
)
Result does not contain options but i see in console there are appropriate DB requests. However it does only works if i use :include inside to_json:
items = Item
.order('id')
.where(manufacturer)
.where('is_active')
render :json => {:data => items.offset(offset), :total => items.count}.to_json(
:include => :options
)
So the first question is what am i doing wrong so that .include does not work?
But i aslo have problem with working code. I need options to be joined with item_options because options just store options name, options group id and so on, when item_options keeps value for defined option for defined item. And so i'm trying to extend my code as follows:
items = Item
.order('id')
.where(manufacturer)
.where('is_active')
render :json => {:data => items.offset(offset), :total => items.count}.to_json(
:include => {
:options => {
:joins => :item_options
}
}
)
But still, i receive options not beeing joined with item_options. Why?
Also if i use joins inside optoins do i need to define has_many through in items if they loaded without additional information in item_options?
========== UPDATE:
For now i just replaced an options relation to method in Items model:
item = Item
.includes(:item_options)
.find(params[:id])
render :json => item.to_json(:methods => :options)
and in Item model:
has_many :item_options
def options
self.item_options.select('item_options.value, options.name, options.is_feature, options.root').joins('left join options on options.id = item_options.option_id')
end
Don't know, however, if this solution is optimal.

Answer 1

Your calling to_json on a hash and not on the model, and Hash knows nothing about includes or joins.
Try putting your json options on the model
data = items.offset(offset).as_json(include: :options)
render json: {data: data, total: items.count}
Also, I think your Option belongs_to :item_options should be Option has_many :item_options
Using :include within as_json is an instruction to the ActiveModel json serializer telling it to include data from associations in the output JSON.
ActiveModel::Serializers::JSON
(github)
The joins and includes methods are part of ActiveRecord and are used to add join conditions and perform eager loading.
ActiveRecord joins
ActiveRecord includes