我的 HAML 模板的这个助手有什么问题?
  def display_event(event)
    event = MultiJson.decode(event)
    markup_class = get_markup_class(event)
    haml_tag :li, :class => markup_class do
      haml_tag :b, "Foo"
      haml_tag :i, "Bar"
    end
  end
这是错误:
haml_tag outputs directly to the Haml template.
Disregard its return value and use the - operator,
or use capture_haml to get the value as a String.
模板调用 display_event 是这样的:
 - @events.each do |event|
     = display_event(event)
如果我使用常规标记,它将扩展到以下内容
%li.fooclass
   %b Foo
   %i Bar