Mapper Snap: Valid Column Names In Input Schema Give "Undefined" Error

[JPaps]

Hi,

I am experiencing an issue where I have a Mapper Snap that gives the error: $[FieldName] is undefined when I input a field name in the expression box.

The fields that I am using are inside the input schema of the mapper snap (I have dragged and dropped) so I know that the fields are valid. I have tried refreshing the page, restarting my browser and clearing cache to eliminate the possibility of it being a browser issue.

Does anyone know what could be the cause of this problem?

[JPaps]

Sure, I will attach screenshots to this response. Please see below;

Error from within the problematic snap after drag and drop:

pipeline overview:

[ptaylor]

You’re not showing us the input data but the error message means that the TAIX-POL field does not exist in some of the input documents. Try either the expression it’s recommending, $.get('TAIX-POL') or avoid the issue more generally by checking the “Null-safe access” box at the top of the Mapper.

[ptaylor]

Are you using quotes around the field name, like this?
$['FieldName']

[JPaps]

Thanks for your help.

Yes, i dragged the field from the input schema and it goes into the expression box with the quotes and brackets but it gives the undefined error

[WhatIsThis]

Might be that you need to enable Null-safe access checkbox