IsValid() returning 1 on non-existent field

[Fakko]

I am writing a script that takes a parameter which is part of a field name (eg. BusDev ) and then builds the field's full name, looping until it generates a field name that doesn't exist.

Completed_BusDev_01 [ perform calculations ]

Completed_BusDev_02 [ perform calculations ]

...repeat...

Until you generate a field that doesn't exist and drop out of the loop.

I have tried to break out of the loop using IsValid (ie. Exit Loop If [ not IsValid($completed)] ) and IsEmpty (ie. Exit Loop If [ IsEmpty($completed) ] ), but neither one works. The loops continue well beyond the existing fields until I break out of the loop manually via a custom dialog option.

So, what am I doing wrong? The included FMPro help for IsValid states that IsValid returns 0/false if the references to the field or parent table are invalid.

Is there any other built-in function that checks if a field exists/is accessible ?

[eos]

Completed_BusDev_01 [ perform calculations ]

Completed_BusDev_02 [ perform calculations ]

...repeat...

What does “perform calculations” mean? Within a script, a field does not stand for itself, but is the target of an action.

Try that action and check if it generates an error code which you can then handle.

[comment]

There is a difference between a field's name as text and a reference to a field. If you have a variable containing text, and you want to know if a field so named exists, try =

IsValidExpression ( $fieldName )

Other than that, it's a bit strange that you need to write a script without knowing which fields you have. Not to mention that numbered fields, such as Completed_BusDev_01, Completed_BusDev_02, etc. are usually a symptom of poor structure. Most likely, you should be using multiple records in a related table instead of the multiple fields. Then it would be also very easy to loop among them, if at all necessary.

[Fitch]

Looks like you're just asking if the variable is valid. That won't tell you anything about a field.

Try this:

Exit Loop If [ not IsValid( GetFieldName( Evaluate( $variable ) ) ) ]

[Fakko]

[ perform calculations ] means I am performing various calculations with the created field variable and other variables.

I realize this is a sub-optimal design, but it's use is small scale for a single individual. It's use requirements changed repeatedly midstream.

The reason for the variance is that there are clusters of related fields that apply based upon a selectable field. I wanted to write a single script that could handle all cases without hard coding each cases' limits and instrad find them programmatically.

I will try your suggestion. Thank you.

Ps. Interesting. I thought the use of a locally defined variable in these functions would use them as their intended field reference and not just a string literal.

Update: Exit Loop If [not IsValidExpression($completed)] gives me the function I am looking for.

Thank you for your help.

[Fitch]

Nice one, Michael. So many functions, so few brain cells...