class Lookbook::PreviewsController

def set_params
  # cast known params to type
  @example.params.each do |param|
    if preview_controller.params.key?(param[:name])
      preview_controller.params[param[:name]] = Lookbook::Params.cast(preview_controller.params[param[:name]], param[:type])
    end
  end
  # set display params
  preview_controller.params.merge!({
    lookbook: {
      display: @example.display_params
    }
  })
end