Trigger observer of parent class on change

I'm writing a timeline, that stores events in a table when there are changes to objects, such as "products".

I've written an observer for Product that composes a sensible log message and associated data using "after_create" and "before_update" and so on. This works perfectly.

Now, each Product has many Variants, and also, each Variant has many Prices. However they are t开发者_开发百科ypically edited in the same form. But only changes to the Product-class cause the observer to trigger "before_update".

I would like changes to Variants to trigger the Product-observer for the associated product, and in the same way cause changes to Prices trigger the product associated with the Variant associated with the Price.

This is not unlike the :touch functionality in Rails 2.3.3+. I've also tried to depend on that function, but the touching does not seem to trigger the before_update observer method.

How would you do this?

Based on my current experience touch should trigger regular callbacks but not observer callbacks. As these are slightly different.