Variant
Variant
Example
procedure NormalizeValue(Input: Variant; var Output: String);
begin
if VarIsNull(Input) or VarIsEmpty(Input) then
Output := ''
else
Output := VarToStr(Input);
end;
Usage
Variant stores a dynamically tagged scalar, Null, Empty or array value whose conversions are validated at runtime.
Additional Technical Info
Variant is PascalScript's dynamically tagged value type (btVariant), backed by Delphi Variant interoperability. It can hold supported numeric, Boolean, date, String/interface values, arrays, Empty or Null.
Empty means uninitialized/no value assigned. Null is an explicit unknown/database-null value. They are distinct from each other, numeric zero, Boolean False and String ''. Test with VarIsEmpty/VarIsNull before strict conversion.
Conversions occur at runtime and can be locale-dependent or raise for incompatible content. Use VarType/VarAsType or a purpose-specific conversion once at the boundary, then keep strongly typed locals. Do not repeatedly rely on implicit coercion in business logic.
Null participates in Variant expressions with propagation/error rules that differ from ordinary values. The modified PascalScript runtime makes one ANSI-string extraction path call VarToStr to avoid a Null conversion exception, but that implementation convenience does not redefine Null as empty. Use explicit Null handling.
Variant arrays have their own bounds and element tags. Use VarArrayCreate/Get/Set and validate dimensions/bounds. A Variant assignment manages/copies its dynamic value; object/interface lifetime still follows the contained type and host boundary.
The example is source-reviewed only; no Variant was converted.
External references
- Embarcadero Variant types - Delphi dynamic value, Empty/Null and conversion model.
- Free Pascal Variants - compatible Variant model and comparison reference.