In the previous article, I showed you how to manage user input in the XForms model. I discussed the process of submitting an XForm and – more importantly - validating user input prior to submission using built-in XML Schema support. In this concluding article, find out how to use the <xforms:bind> element to perform calculations on form input values, integrate XPath expressions into your XForms model and get a crash course in the XForms event model.
In the previous article, I showed you how to manage user input in the XForms model. I discussed the process of submitting an XForm and – more importantly - validating user input prior to submission using built-in XML Schema support.
In this concluding segment, I'll introduce you to some of XForms' more arcane features. First, the concept of binding, which allows developers to implement a number of useful features quickly: calculating values instantly, enforcing basic validation rules, taking decisions on the fly, or rendering a particular node non-writable.
Next, I'll briefly show you how you can use XPath functions within an XForms model definition, and illustrate how functions like sum() and avg() allow you to perform complex calculations in a simple and smooth manner. I'll also take a quick look at the XForms event processing model, explaining the important phases and showing you a basic example of how triggers and actions work.
