如果<span>存在条件，如何将样式应用于 ，如果 Rails 3 中不存在，则将其删除？

Question

span 标记当前如下所示：

<span class='best_in_place<%= ' list-downvoted' if upload.downvoted? %><%= ' list-upvoted ' if upload.upvoted? %>'

但是，如果此跨度既被否决又被点赞，则它应用这两种样式。

我如何修改它以仅应用一个，如果另一个确实存在，则删除另一个？

即，如果此项目之前被否决，则删除list-downvoted类，反之亦然。

编辑：在我的UploadsHelper中添加了推荐的代码

module UploadsHelper
    def best_span_class_for_upload(upload)
      # Start with the base style
      css_class = 'best_in_place'
      # Add on any conditional styles using String#<< concatenation
      css_class << ' list-downvoted' if (upload.downvoted?)
      css_class << ' list-upvoted' if (upload.upvoted?)
      # Return the result
      css_class
    end
end

跨度现在看起来像这样：

<span class='<%= best_span_class_for_upload(upload) %>' id='best_in_place_upload_name' data-url='<%= upload_path(upload) %>' data-object='upload' data-attribute='name' data-formType='input' data-activator='span#upload-edit-name-<%= upload.id %>'><%= upload.name %></span>

Answer 1

最好汇总

到一个帮助程序方法中，以避免弄乱模板：

<span class='<%= best_span_class_for_upload(upload) %>'>

然后，在helper/定义的模块中定义的帮助程序方法将如下所示：

def best_span_class_for_upload(upload)
  # Start with the base style
  css_class = 'best_in_place'
  # Add on any conditional styles using String#<< concatenation
  css_class << ' list-downvoted' if (upload.downvoted?)
  css_class << ' list-upvoted' if (upload.upvoted?)
  # Return the result
  css_class
end

更新：

仅显示向上或向下之一的修订版本：

def best_span_class_for_upload(upload)
  # Start with the base style
  css_class = 'best_in_place'
  # Add on any conditional styles using String#<< concatenation
  if (upload.downvoted?)
    css_class << ' list-downvoted' 
  elsif (upload.upvoted?)
    css_class << ' list-upvoted'
  end
  # Return the result
  css_class
end