Question

基本上我想做的是检查方法是否在对象上返回true，如果是，则将特定类应用于图像。

如果没有，那就什么都不做。

所以我尝试了这个：

<%= image_tag(upload.image.url, if upload.upvoted? :class => 'upvoted') %>

但这是我得到的错误：

/app/views/stages/compare.html.erb:29: syntax error, unexpected ')', expecting keyword_then or ';' or '\n'
...d.upvoted? :class => 'upvoted') );@output_buffer.safe_concat...
...                               ^
/app/views/stages/compare.html.erb:31: syntax error, unexpected keyword_end, expecting ')'
');              end                        
                    ^
/app/views/stages/compare.html.erb:63: syntax error, unexpected keyword_ensure, expecting ')'
/app/views/stages/compare.html.erb:65: syntax error, unexpected keyword_end, expecting ')'

Answer 1

<%= image_tag(upload.image.url, :class => upload.upvoted? ? 'upvoted' : nil) %>

Answer 2

正如我在评论中所说，我会将确定类的逻辑移动到辅助方法：

module StageHelper
  def upload_class(upload)
    if upload.upvoted?
      'upvoted'
    elsif upload.downvoted?
      'downvoted'
    end
  end
end

然后您的图片代码帮助将是：

<%= image_tag(upload.image.url, :class => upload_class(upload) %>

如何在Rails 3中的image_tag助手中执行if语句？

2 个答案: