Formulas and Custom Functions

[kutoose]

Application : Crystal Reports 10

I was trying to create a custom function from a formula using extractor. The formula was having an 'isnull' function. I got the following error message :

A custom function can not be extracted from this formula.

The formula contains functions that can not be used in custom functions.
isnull



Have any one come across this ? What is a solution ?

kutoose@yahoo.com

 

[bdreed35]

I found this blurb in the help files:

Custom function syntax rules
Due to the independent nature of custom functions, there are some limitations:

You cannot use report or database fields, including summary fields, in a custom function.
You cannot use shared or global variables in a custom function, but you can pass a global or shared variable in as an argument when calling a custom function from within a formula.
You cannot use recursion, either direct or indirect, in a custom function.
You cannot directly use UFLs in a custom function.
You cannot call Evaluation Time, Print State, or Document Properties functions. Also, you cannot use the functions: Rnd, CurrentFieldValue, DefaultAttribute and GridRowColumnValue.
These restrictions are designed to make custom functions independent of the report they are being used in.

IsNull is a Print Time formula. I am going to see if I can determine a workaround.

~Brian

 

[kutoose]

Thanks Brian - Let us know if there is a workaround.

kutoose@yahoo.com

 

[bdreed35]

This may or may not work for you. The basic idea is to move check for the NULL's before you call the custom function.

I set my formula up like this to check for NULL's, and to return a default character to the custom function that I can test for.

if isnull({table.field}) then
    myCustomFunction ("/")
else
    myCustomFunction ({table.field})

In the Custom Function, check for the character instead of checking for IsNull(). I know this requires a littel more work for each report, but hopefully it helps get the bulk of the logic into the function.

~Brian

 

[kutoose]

Umm..
Let me try this. Looks cumbersome.

Thanks !

kutoose@yahoo.com