How to use Application Helpers in Ruby on Rails

Question

I'm attempting to post a random testimonial on each page of a site. I started off by using an application helper like so:

module ApplicationHelper

  def random_testimonial
    @random_testimonial = Testimonial.find(:first, :offset => rand(Testimonial.count))
  end

end

In my view, I can reference the method but it's being called on each reference, which makes sense. Instead, I'd like this to be called once on each page view, exposing a Testimonial object I can use within the view. What should I be looking for to do this?

Answer 1

If I understand you correctly, you want a method that returns the same object every time it is referenced in one request/response cycle. If this is true, you can achieve it with a minor change to your helper:

 def random_testimonial
    @random_testimonial ||= Testimonial.find(:first, :offset => rand(Testimonial.count))
 end

Notice the "||=" part. That's a Ruby idiom which says: assign a value to @random_testimonial, unless it already has a value.

Hope that answers your question.

Answer 2

Thank you, that did the trick!

Answer 3

While that works, and I have certainly been known to do this, it violates the MVC separation of concerns. View helpers are not supposed to contain controller/model type logic, which this does.

You might consider refactoring this back into the application controller. Helpers are supposed to be for view formatting and stuff, more than as a function (which is what I kept wanting to do when I got started.)

If you got back into your Testimonail model, do could do

def self.random
  Testimonial.find(:first, :offset => rand(Testimonial.count))
end

then in your application controller, you could do:

def random_testimonial
  @random_testimonial ||= Testimonial.random
end

and call it from a before_filter

This has the advantage of moving the database logic back into the model where it belongs.