Rails 3.1. What's the easiest way to make chaining dropdown selects?

I was trying to make work this: http://chainselects.hypermediasoft.com/

But got error:

Routing Error
uninitialized constant ChainSelectsHelper

So i have to make so开发者_运维知识库me break and ask community - is there any easy way to make chaining select boxes for my application forms?

UPDATE:

Maybe i should make editions in some config files? I can see thist ChainSelectsHelper in vendor/plugins/ChainSelects/lib/app/helpers/chain_selects_helper.rb. But why my application can't see this? Any assets pipeline configs needed?

And got this error in model:

undefined method `acts_as_chainable' for #<Class:0x007fe387542780>

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From the looks of it, it seems that you did not add this in the controller:

include ChainSelectsHelper

Keep in mind that modifications have to be made to both model and controller, as stated here.