Delphi in a Nutshell

Name

TVarData Type

Syntax

type
  TVarData = packed record
    VType: Word;
    Reserved1, Reserved2, Reserved3: Word;
    case Integer of
      varSmallint: (VSmallint: Smallint);
      varInteger:  (VInteger: Integer);
      varSingle:   (VSingle: Single);
      varDouble:   (VDouble: Double);
      varCurrency: (VCurrency: Currency);
      varDate:     (VDate: Double);
      varOleStr:   (VOleStr: PWideChar);
      varDispatch: (VDispatch: Pointer);
      varError:    (VError: LongWord);
      varBoolean:  (VBoolean: WordBool);
      varUnknown:  (VUnknown: Pointer);
      varByte:     (VByte: Byte);
      varString:   (VString: Pointer);
      varAny:      (VAny: Pointer);
      varArray:    (VArray: PVarArray);
      varByRef:    (VPointer: Pointer);
  end;

Description

The TVarData record is Delphi’s implementation of the Variant type. You can cast any Variant to TVarData to examine the internal workings of the Variant.

The VType field stores the variant type (as returned by VarType). The other fields store type-specific information. Values up to 8 bytes in size are stored directly in the TVarData record. Larger items are stored separately; the TVarData record holds a pointer to the actual data (such as VArray, which points to a TVarArray record).

Tips and Tricks

• VString is actually a string type, but Delphi does not let you store a string in a variant record because it cannot initialize or finalize the record properly. Instead, the code that manages the Variant takes care of initializing or finalizing the string.

• VUnknown is actually an IUnknown interface, and VDispatch is an IDispatch interface. As with strings, Delphi ...