How do I apply one of two classes to an image depending on a certain condition in Rails 3?

问题

So for one class, I would do something like:

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

But I want to have it check to see if downvoted applies, and if so applies the class downvoted'. If it doesn't apply, it checks to see ifupvoted` does, and then applies that class.

回答1:

I would move the logic for determining the class to a helper method:

apps/helpers/stage_helper.rb

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

Then your image tag help would be:

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

来源：https://stackoverflow.com/questions/5384369/how-do-i-apply-one-of-two-classes-to-an-image-depending-on-a-certain-condition-i