User Guide

Best practices for Flash forms 707
Best practices for Flash forms
The following sections describe best practices that can help you increase the performance of Flash
forms.
Minimizing form recompilation
Flash forms are sent to the client as SWF files, which ColdFusion must compile from your CFML
code. The following techniques can help limit how frequently ColdFusion must recompile a
Flash form.
• Only data should be dynamic. Whenever a variable name changes, or a form characteristic,
such as an element width or a label changes, the Flash output must be recompiled. If a data
value changes, the output does not need to be recompiled.
• Use cfformgroup type="repeater" if you must loop no more than ten times over no more
than ten elements. This tag does not require recompiling when the number of elements
changes. It does have a processing overhead that increases with the number of loops and
elements, however, so for large data sets or many elements, it is often more efficient not to use
the repeater.
Caching data in Flash forms
The
cfform tag timeout attribute specifies how many seconds ColdFusion retains Flash form
data on the server. When a Flash form is generated, the values for the form are stored in memory
on the server. When the Flash form is loaded on the client, it requests these form values from the
server. If this attribute is 0, the default, the data on the server is immediately deleted after the data
has been requested from the Flash form.
A Flash form can be reloaded multiple times if a user displays a page with a Flash form, goes to
another page, and uses the browser Back button to return to the page with the form. This kind of
behavior is common with search forms, login forms, and the like. When the user returns to the
original page:
• If the timeout value is 0, or the timeout period has expired, the data is no longer available, and
ColdFusion returns a data-expired exception to the browser; in this case, the browser typically
tells the user to reload the page.
• If the timeout has not expired, the browser displays the original data.
If your form data contains sensitive information, such as credit card numbers or social security
numbers, you should leave the timeout set to 0. Otherwise, consider setting a timeout value that
corresponds to a small number of minutes.