DRYer XML/JSON response logic

api_formats.rb

module ApiFormats
  API_FORMATS = %w[json xml].map(&:to_sym).freeze

  def self.included(base)
    base.send :private, :api_formats
  end

  def api_formats(format, data=nil, options={})
    API_FORMATS.each do |encoding|
      format.send(encoding) do
        if block_given?
          yield
        else
          render options.merge(encoding => data)
        end
      end
    end
  end
end

examples.md

Instead of

respond_to do |format|
  format.html # show.html.erb
  format.xml  {render :xml  => @item}
  format.json {render :json => @item}
end

Use

respond_to do |format|
  format.html
  api_formats format, @item
end

Takes options

api_formats format, @item,                                     
  :status => :created, :location => @item

And blocks

api_formats(format) {head :ok}