I have a form that users are allowed to enter time values in (say, hours spent performing some task). A business requirement is that the time be entered in either hh:mm format, or decimal format. In either case, there could potentially be quite a bit of client side javascript for display "helping"--showing totals, validating against other input, etc.
So, for instance, one user might enter "8:30" for Eight Hours Thirty Minutes, while another might enter "8.5" to mean the same thing. I'm looking for something that would let me keep the form/validation duplication to a minimum.
What are the best ways to go about this with the model and the view?
The regular expression to allow both formats wouldn't be that complicated. I would perform that simple validation client-side via javascript. Beyond that, you may want to add some business validation (at the business object level) for this.