I was having trouble munging JSON data from a Rails API into a format that Ember would accept. This is what worked for me. I also used the active_model_serializers gem, but I think it was unnecessary for this simple example.

gistfile1.rb

# /app/controllers/api/v1/articles_controller.rb

# ...

def index
  @articles = Article.all

	respond_to do |format|
		format.json { render json: @articles, :callback => params[:callback] }
	end
end

# ...


# In EmberJS
# source = "http://localhost:3000/api/v1/articles.json?callback=?"
# => jQuery1910899980530841276_1369269371244({"articles":[{"title":"Article","body":"Lorem"},{"title":"Post","body":"Praesent"}]})