How do I make my app respond to a format based on a querystring parameter?

Question

For example, I would like

/apples/123?_format=json

to act like

/apples/123.json

where it renders the *.json.* templates, executes respond_to {|format| format.json {...}}, etc.

Is this at all possible?

Thanks!

Answer 1

You can do the following to disable Rails' automatic handling of the .ext format:

constraints format: false do
  resources :apples
  # ...
end

Then, and this is a bit gross but I don't see a better way to do this at the moment, you can do the following to update ActionController on what format to serve:

class ApplicationController < ActionController::Base
  before_filter :set_format_from_query_string

private

  def set_format_from_query_string
    request.format = params.fetch(:_format, 'json')
  end
end

This will allow your respond_to block to toggle based on the _format query string parameter and uses json as the default format.