Rendering json from two models in Rails index - ruby-on-rails

Question

I would like to render json in an index method that joins data from a foreign-key related table in Rails. I have a model that has user_id as a foreign key.
class Batch < ActiveRecord::Base
belongs_to :user
I am then rendering that table and exposing the user_id field.
def index
panels = Batch.where("user_id = #{current_user.id} or (user_id <> #{current_user.id} and public_panel = true)")
render json: panels, only: [:id, :description, :name, :public_panel, :updated_at, :user_id], root: false
end
What I would like to do is to somehow expose the users name, which is on the Users model. ie: user_id.user_name
EDIT
From reading documentation, I think I need to use include but would also like to alias one of the fields. I have a field called name in both tables.
Something is wrong with this include
def index
panels = Batch.include([:users]).where("user_id = #{current_user.id} or (user_id <> #{current_user.id} and public_panel = true)")
render json: panels, only: [:id, :name, :description, :public_panel, :updated_at, :user_id], root: false
end
EDIT2
Thank you #Paritosh Piplewar ... I am getting some errors with the syntax. To complicate matters the field I am after is user.name, not user.user_name. This will conflict with batches.name, so I need to alias it.
Started GET "/api/batches" for 10.0.2.2 at 2014-08-13 15:39:03 +0200
SyntaxError (/home/assay/assay/app/controllers/api/batches_controller.rb:11: syntax error, unexpected tLABEL
user: { only: :first_name },
^
/home/assay/assay/app/controllers/api/batches_controller.rb:11: syntax error, unexpected ',', expecting keyword_end
user: { only: :first_name },
^
/home/assay/assay/app/controllers/api/batches_controller.rb:12: syntax error, unexpected ',', expecting keyword_end):
EDIT 3
The original question has been answered, but the json returned is like this
data: [{"id"=>1306, "updated_at"=>Wed, 13 Aug 2014 12:37:23 UTC +00:00, "description"=>"asc", "user_id"=>1, "public_panel"=>true, "user"=>{"name"=>"Joe Bloggs"}}, {"id"=>1307,
This bit is causing problems for my Angular.js front-end.
"user"=>{"name"=>"Joe Bloggs"}}

Answer 1

i assume you mean user.user_name
this is how you can do it
def index
panels = Batch.where("user_id = #{current_user.id} or (user_id <> #{current_user.id} and public_panel = true)")
data = panels.as_json(include:
{user: { only: :name }},
only: [:id, :description, :public_panel, :updated_at, :user_id],
root: false)
render json: data
end

Answer 2

You can define custom method and do it. Something like this
class Batch < ActiveRecord::Base
belongs_to :user
def user_name
user.name
end
end
Now, in controller you can simply do this
def index
panels = Batch.where("user_id = ? or (user_id <> ? and public_panel = true)", current_user.id, current_user.id)
data = panels.as_json(methods: :user_name,
only: [:id, :description, :public_panel, :updated_at, :user_id, :user_name],
root: false)
render json: data
end

Answer 3

For more complex json views than just redering a single model, I'd tell you to use jbuilder. Jbuilder is now part of the rails framework.
It's as easy as
Remove render line and make panels an instance variavle (#panels)
Create a index.json.jbuilder file under app/views/api/batches
Create the view you want
json.array #panels do |panel|
panel.(panel,
:id,
:description,
:public_panel,
:user_id,
:updated_at
)
json.user panel.user.user_name
end