Database Reference
In-Depth Information
ably find yourself using some of the same calculations over and over again. Enter the custom
function. With a custom function, you can centralize oft-used calculations and avoid rewrit-
ing them (and introducing errors) again and again. Better still, if you have to make a change
to your calculation weeks or months after it was created, you won't have to track down and
modify it in every place you used it. Just change the custom function, and the update ripples
through your database instantly. To create and edit custom functions, you need FileMaker
Pro Advanced.
You create custom functions in the Manage Custom Functions dialog box (
Figure 13-14
).
Custom functions have to follow the same syntax as FileMaker's regular functions. That is,
you provide a name and, optionally, one or more parameters.
Figure 13-14. The Manage Custom Functions window (File→Manage→Custom Functions) is
where you go to create your own functions. It shows a list of any custom functions you've defined,
plus buttons for creating, editing, duplicating, deleting, or importing custom functions. As usual,
you can sort the list by making a choice from the “View by” pop-up menu. Finally, when you're all
done, click OK to save all your changes or Cancel to close the window and ignore any changes
you've made.
Rules for custom function names and their parameters are similar to the rules for naming
tables and fields. Specifically, function and parameter names may not:
▪ Contain
+ - * / ^ & = ≠ < > ≤ ≥ ( , ; ) [ ]
″
:: $ {}
▪ Contain
AND
,
OR
,
XOR
,
NOT
▪ Begin with a digit or period
▪ Have the same name as another function, parameter, or keyword
