How to merge another field in object in rails json response

First merge {:video_url => @ad.video.url } with @ad then do following:

{:ad =>  @ad.attributes.merge( :video_url => @ad.video.url )}

so your render call would look like following:

render json: {:success=>true, :message=>"Ad detail", ad:  @ad.attributes.merge( :video_url => @ad.video.url )}, :status=>200  

You may need to use @ad.attributes.except("created_at",....) at following code if you don't need some of the attributes of your active record object @ad.

Just before render define the object to send (note that if @ad is not a hash, probably it should be converted to hash before):

#                    ⇓⇓⇓⇓⇓⇓⇓ this depends on what @ad currently isobject_to_send = @ad.to_hash.merge(video_url: @ad.video.url)

and then:

render json: { success: true,                message: "Ad detail",               ad: object_to_send },        status: 200

You could use the as_json method, but you need a method that returns the URL directly

class Ad  def video_url    video.url  endend

Then in the render

render json: {  success: true,   message: "Ad detail",  ad: ad.as_json(    only: {      :id, :title, :description, :video_file_name, :thumbnail_file_name, :campaign_id, :duration    },    methods: :video_url  ),   status: 200

of course if you want you could wrap this into some method,

class Ad  def my_video_json    as_json(      only: {        :id, :title, :description, :video_file_name, :thumbnail_file_name, :campaign_id, :duration      },      methods: :video_url    )  endend

Then the render would look like this

render json: { success: true, message: "Ad detail", ad: ad.my_video_json }, status: 200