[nagnatron]

You're right that it's similar to extracting it to a module since (in this example) HashGenerator.new is evaluated with the class and in my Request spec I can't exactly stub HashGenerator.new to return a double.

How would you do it?

[camwest]

Create a RequestFactory which is responsible for creating valid requests, put the hash generator in there. Then use the factory in the controller instead of directly creating the model.

That way you don't have the indirection of an ActiveRecord callback and you have your process of creating a request and assigning it a unique hash in a straightforward single process.

[nagnatron]

This makes sense. Thanks.

[camwest]

I've learned this the hard way. I have an app which has callback chains through 5+ models and it's basically impossible to figure out what's going on.

-C

[JonWood]

I'm starting to use service objects, which are responsible for coordinating things when multiple models are required to perform an operation, or complex business logic is involved.

James Golick has a great blog post on that approach at http://jamesgolick.com/2010/3/14/crazy-heretical-and-awesome...