Besides the functions of TVariant and the intrinsic type helper, there is a style of test that you will find throughout the RTL. This is the "not null" test, and it can be a bit confusing when coming straight from Delphi or Freepascal. The test literally checks that a variant is "not null" -but, it doesn't check if the variant is unassigned, so it must be used with care:


// Check that FHandle is "not null"

if (FHandle) then

begin

end;


This type of testing is typically done inside visual controls (or Node.js libraries), where you explicitly know the full life-cycle of a reference.

It's worth mentioning since you will encounter it often.