til/rails/respond-with-json-regardless-of-content-type.md

Respond With JSON Regardless Of Content Type

Let's say you want to serve some JSON from an endpoint (for example, you might be serving the apple-app-site-association file for iOS Universal Links). Regardless of whether the endpoint is requested as JSON (application/json), HTML (text/html), or something else (plain/text), you want to respond with JSON.

The format#any method can be used when defining the respond_to block. This tells the controller that any mimetype is accepted.

def show
  respond_to do |format|
    format.any do
      render params[:page],
        formats: 'json',
        content_type: "application/json",
        layout: false
    end
  end
end

The other important element in this is formats: 'json' which helps Rails find your <template_name>.json.erb file in the views directory.

Though I cannot find any documentation for it, format.all appears to work the same as format.any as described in the above example.

h/t Dillon Hafer