On the QaFoo blog they have a new post offering some advice on extracting functionality to data objects and reducing the complexity of your application's interfaces.

Extracting data objects from your code will make it easier to read and write, easier to test and more forward compatible. This post shows you the two most common cases where introducing a data object makes sense and how to do it.

The first case covers the extraction when a method ends up with too many parameters. We've all been there and remembering the correct order and values for each (not to mention optional vs required). By making use of value objects you can reduce that down to one or two parameters that act as self-contained "containers" for the same values. They illustrate with a refactor of "product" search criteria into a "ProductCriteria" object. The second example show a refactor away from using an array as an input value and providing a bit more structure with a "Checkout" value object instead.

The post ends with a helpful hint about migrating from one method to the other in legacy systems using a "shim" method to handle the new case right alongside the old one.