> Take some elements from the form and search for an add in the past
> <time period>. We did one recently where we took the email address,
> recipient and amount from the form and then made sure that the same
> data hadn't already been submitted in the last 24 hours - working on
> the principle that a user is unlikely to gift the exact same amount to
> the same person on the same day. The check is trivial compared to the
> commit.
>
> FWIW, we looked into this and this approach seemed to be the quickest
> and most reliable available. If you Google on this, you may find an
> article or two which support this approach.
This does seem workable and reliable. I suppose I'm hoping for an
approach that can easy re-used across many forms, without much per-form
effort required.
Also, I think for some kinds of changes being submitted, the check of
"has this happened recently" won't apply.
For example, we allow people to re-order a list of photos. They may well
reverse the ordering a few seconds later and put the photos back in the
original order. (Although that example may not be vurnerable to a
double-submit bug, as it would be valid to submit the same ordering
request twice. )
Mark
