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IsNullZero

function IsNullZero: Boolean

Example​

procedure ScriptEvent(var Value: variant);
begin
  if Field.IsNullZero then
    Value := 'Missing or zero'
  else
    Value := Field.Value;
end;

Usage​

IsNullZero applies Velox's type-dependent null-or-zero sentinel test to the current field value.

Important distinctions

  • Boolean false is numeric zero and returns true because ftBoolean is in the numeric set.
  • Velox date/time value 0 returns true; that value represents the Velox epoch/midnight rather than database null.
  • A numeric field containing zero returns true even though Null returns false.
  • A string field containing '0' returns false; nonnumeric fields are tested only for trimmed empty text.
  • Null/Empty/Clear are treated alike even though they are distinct Variant states.
  • Types omitted from the numeric set use the string branch even if they support some numeric conversion.

Variant comparison or VarToStr can raise for unsupported/custom values such as some arrays. Field access can also raise if the field/dataset is invalid. The method does not write or navigate.

Use SetIfZero to assign under the same condition and NotNullZero for the exact negation.

Additional Technical Info​

IsNullZero reads GetAsVariant once, then applies one of two rules selected by Velox's hard-coded field-type groups.

Field categoryReturns true when
IsNumericType or IsDateTypeVariant is Null, Empty or Clear, or compares equal to numeric zero
every other DataTypeTrim(VarToStr(Value)) = ''

The explicit date check is redundant in the current source because all four date types are also in the numeric set, but it records the intended date-sentinel behavior.

External references

Created 2026-07-15