如何在Rails 3中的image_tag助手中执行if语句？

Question

基本上我想要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) %>