Input Box variable always showing IsNull as False in Qlik sense

[vsabbise]

Hi,

I have an input box with a variable vWord and for some reason if(IsNull(vWord),'T','F') always returns F though I don't enter any values in the input box. 

I am not sure what's causing that. I checked the definition of the variable and intentionally I left it blank.

[marcus_sommer]

Blank/Empty isn't NULL - therefore try it with:

if(len(trim('$(vWord)')) = 0,'T','F')

- Marcus

[sidhuchocky]

Hi,
Your logic is correct but the syntax is incomplete.
Try this ,
If(IsNull(vWord) = -1 ,'T','F')
This return 'T' if vWord is NULL and 'F' otherwise .

[marcus_sommer]

It's not mandatory necessary to compare isnull() or similar checkings with = -1 or = 0 because 0 will be always treated as FALSE and each other numerical value is TRUE and therefore the above logic with: if(isnull(var), then else) will work and the issue will be either the variable-call or that isnull() expects a real NULL and not empty/blank/any spaces.

- Marcus