I wanted to warn application developers of a fundamental issue with formula fields. Formula fields do not get updated when the value of fields they refer to are updated via script.

Create a simple form with 3 fields:

1. Drop Down list– ‘Drop Down 1’ - with a script on user input to increment a numeric field by 1 - input.Number_1 = (input.Number_1  +  1);
2. Numeric field – ‘Number_1’ - with default value of 1
3. Formula field – ‘Formula_1’ - with expression “Number_1” setting it equal to the numeric field. Make it visible on the form.
   

Now access your form.

Change the numeric field directly and you will notice that the formula field updates as expected.

Select a drop down value you will notice that the numeric field updates but the formula field remains unchanged when it should update to the value within the numeric field.

I reported this issue in June 2012 and was told 6 months later that it would not be fixed (see response below). I can confirm that ZoHo are true to their word as it is still not fixed.

Hello Ben,

Please accept our apologies for failing to contact you earlier about this fix.
There are multiple design problems that prevent us from ensuring formulas or other field types are kept updated as a result of a script action. Application performance problems may also arise if this is fixed. Therefore this problem is not possible to resolve, at least at this point of time.

Any inconvenience caused is regretted.

Regards,
Akash
Zoho Creator

The response acknowledges that application developers can not be guaranteed of data integrity when using formula fields.

This is a great disappointment to me for the ZoHo Creator platform as it is fundamental requirement that formula fields maintain their integrity at all times.

Please beware of this fault in the platform.