Rails Object Relationships and JSON Rendering
Solution 1
By default you'll only get the JSON that represents modelb
in your example above. But, you can tell Rails to include the other related objects as well:
def export
@export_data = ModelA.find(params[:id])
respond_to do |format|
format.html
format.json { render :json => @export_data.to_json(:include => :modelb) }
end
end
You can even tell it to exclude certain fields if you don't want to see them in the export:
render :json => @export_data.to_json(:include => { :modelb => { :except => [:created_at, updated_at]}})
Or, include only certain fields:
render :json => @export_data.to_json(:include => { :modelb => { :only => :name }})
And you can nest those as deeply as you need (let's say that ModelB also has_many ModelC):
render :json => @export_data.to_json(:include => { :modelb => { :include => :modelc }})
If you want to include multiple child model associations, you can do the following:
render :json => @export_data.to_json(include: [:modelA, :modelB, :modelN...])
Solution 2
If you want a more flexible approach to rendering json, you can consider using the gem jbuilder: https://github.com/rails/jbuilder
It allows you to render custom attributes, instance variables, associations, reuse json partials in a convenient way.
Comments
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M. Ryan over 3 years
Disclaimer, I know very little about Rails. I'll try to be succinct. Given the following model relations in Rails:
class ModelA < ActiveRecord::Base belongs_to :ModelB ... class ModelB < ActiveRecord::Base has_many :ModelA
When calling the show action of the ModelA controller the returned JSON should show all ObjectAs that are children of the ObjectB of which the ObjectA in question is a child of.
So if I have an ObjectB that contains ObjectA's of ID 1, 2 and 3 and then access: /modela/1.json
I should see:
{ "modelb": { "id": "1", "modela": [insert the ModelA JSON for ID's 1, 2 and 3] } }
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Brian almost 14 yearscan you share your controller code (especially the query being performed)?
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M. Ryan almost 14 yearsThe controller is huge. The query is just @tour = Tour.find(params[:id])
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M. Ryan almost 7 yearstesttesttesttest
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Automatico almost 11 yearsIf you want more than one include you add the as an array:
@whatever.to_json(include: [:modelA, :modelB, :modelN...])
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Scalahansolo about 10 yearsIf I wanted to call this export function within a view to pull attributes from a specific model, how would I call this?
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Piccolo about 4 yearsAnd what would be the approach, if only ModelA width ID=2 should be included? Is there any other filtering method?