When Domino developers first start exploring XPages, they naturally tend to compare the new XPages controls and functionality with traditional IBM Lotus Notes and Domino development: “I know what I want to do and how I would have accomplished it with Domino Designer. Now how do I do it in XPages?”

Take the concept of a Notes computed subform. I have heard many developers asking how this is handled in XPages. While many Notes concepts are handled the same way in XPages as in traditional Notes development, the computed-subforms concept is not one of them.

The XPages design component that most closely corresponds with subforms is the custom control. You use a custom control where you have a group of fields or functionality that you want to reuse on other XPages within your application. Once created, a custom control shows up in the Controls palette. Then you can drag and drop the control onto any XPage in your application.

In Notes, you can compute which subform to include on a form based on a formula. Computing which subform to include at runtime is an easy way to tailor the form and functionality without having to maintain numerous hide/when formulas. This is a very valuable feature for rapid application development. With XPages, however, there is no computed custom control. I’ll show you a technique to help you get functionality in XPages that is similar to computed subforms.