Override rails helpers with access to original

问题

I want to use rails' familiar helpers, but with slightly altered functionality. The way I see it, I want to be able to do something like:

module AwesomeHelper
  #... create alias of stylesheet_link_tag to old_stylesheet_link_tag
  def stylesheet_link_tag(*args)
    if @be_awesome
      awesome_stylesheet_link_tag *args
    else
      old_stylesheet_link_tag *args
    end
  end
end

The way I see it, I have three options:

Monkey patching: Reopening the rails helper module. If the rails team ever change the name of their helper module, my code becomes a source of brittleness. Not insurmountable, but not ideal.
Use different method names: Trying to stick to the common rails interface may be my downfall. My changes may become a source of confusion for other developers
Detaching methods (new): Not sure whether this would work, or whether it would have the same drawbacks as 1. Will research this, but this might be a good starting point.

So the question here is, am I stuck with one of these sub-optimal solutions, or is there another way that I haven't considered? If I go for option 3, is there a way to do it without directly addressing the rails helper module?

(Note: I have removed the context, as it adds nothing to the question.)

回答1:

There's a better way than any of your listed options. Just use super:

module AwesomeHelper
  def stylesheet_link_tag(*sources)
    if @be_awesome
      awesome_stylesheet_link_tag *sources
    else
      super
    end
  end
end

Overriding stylesheet_link_tag in AwesomeHelper will ensure that, when stylesheet_link_tag gets invoked, Ruby will encounter it in the method lookup path before it hits ActionView::Helpers::AssetTagHelper. If @be_awesome is true, you get to take charge and stop things right there, and if not, the call to super without parentheses will transparently pass through all the arguments up to the Rails implementation. This way you don't have to worry about the Rails core team moving things around on you!

回答2:

I don't use this gem, so I'll answer you in a more generic way.

Let's say you want to log calls to link_to helper (yeah, contrived example, but shows the idea). Looking in API gives you understanding that link_to located inside the ActionView::Helpers::UrlHelper module. So, you create some file in your, say, config/initializers directory with the following contents:

# like in config/initializers/link_to_log.rb
module ActionView::Helpers::UrlHelper

    def link_to_with_log(*args, &block)
        logger.info '**** LINK_TO CALL ***'
        link_to_without_log(*args, &block) # calling the original helper
    end

    alias_method_chain :link_to, :log
end

The core of this functionality -- alias_method_chain (clickable). Use it AFTER defining the method xxx_with_feature.

回答3:

Try using alias_method:

module AwesomeHelper
  alias_method :original_stylesheet_link_tag, :stylesheet_link_tag

  def stylesheet_link_tag(*sources)
    if @be_awesome
      awesome_stylesheet_link_tag *sources
    else
      original_stylesheet_link_tag *sources
    end
  end
end

回答4:

I would really encourage you to consider your option #2, overriding the behavior of rails methods in a way that is obvious to the caller.

Your new method should be called awesome_stylesheet_link_tag so that other Rails devs can read your code and ask the question "What is so awesome about the link tag?".

As a smaller change you could do the override but pass in :awesome => true as an argument so they at least have a clue that something is afoot.

Changing the behavior of a widely used method like stylesheet_link_tag creates a potential future misunderstanding where none is needed.

来源：https://stackoverflow.com/questions/10471535/override-rails-helpers-with-access-to-original

标签

ruby-on-rails

ruby

overriding

helpers