Valid Types

In the Type Library editor, you use different type identifiers, depending on whether you are working in IDL or Delphi. Specify the language you want to use in the Environment options dialog.

The following types are valid in a type library for COM development. The Automation compatible column specifies whether the type can be used by an interface that has its Automation or Dispinterface flag checked. These are the types that COM can marshal via the type library automatically.

Delphi type	IDL type	variant type	Automation compatible	Description
Smallint	short	VT_I2	Yes	2-byte signed integer
Integer	long	VT_I4	Yes	4-byte signed integer
Single	single	VT_R4	Yes	4-byte real
Double	double	VT_R8	Yes	8-byte real
Currency	CURRENCY	VT_CY	Yes	currency
TDateTime	DATE	VT_DATE	Yes	date
WideString	BSTR	VT_BSTR	Yes	binary string
IDispatch	IDispatch	VT_DISPATCH	Yes	pointer to IDispatch interface
SCODE	SCODE	VT_ERROR	Yes	Ole Error Code
WordBool	VARIANT_BOOL	VT_BOOL	Yes	True = -1, False = 0
OleVariant	VARIANT	VT_VARIANT	Yes	Ole Variant
IUnknown	IUnknown	VT_UNKNOWN	Yes	pointer to IUnknown interface
Shortint	byte	VT_I1	No	1 byte signed integer
Byte	unsigned char	VT_UI1	Yes	1 byte unsigned integer
Word	unsigned short	VT_UI2	Yes*	2 byte unsigned integer
LongWord	unsigned long	VT_UI4	Yes*	4 byte unsigned integer
Int64	__int64	VT_I8	No	8 byte signed integer
Largeuint	uint64	VT_UI8	No	8 byte unsigned integer
SYSINT	int	VT_INT	Yes*	system dependent integer (Win32=Integer)
SYSUINT	unsigned int	VT_UINT	Yes*	system dependent unsigned integer
HResult	HRESULT	VT_HRESULT	No	32 bit error code
Pointer		VT_PTR -> VT_VOID	No	untyped pointer
SafeArray	SAFEARRAY	VT_SAFEARRAY	No	OLE Safe Array
PAnsiChar	LPSTR	VT_LPSTR	No	pointer to Char
PChar	LPWSTR	VT_LPWSTR	No	pointer to WideChar
PWideChar	LPWSTR	VT_LPWSTR	No	pointer to WideChar

Word, LongWord, SYSINT, and SYSUINT may be Automation-compatible with some applications.

See safe arrays for more information about the SAFEARRAY Variant type.

Note: The Byte (VT_UI1) is Automation-compatible, but is not allowed in a Variant or OleVariant since many Automation servers do not handle this value correctly.

Besides these IDL types, any interfaces and types defined in the library or defined in referenced libraries can be used in a type library definition.

The Type Library editor stores type information in the generated type library (.TLB) file in binary form.

If a parameter type is specified as a Pointer type, the Type Library editor usually translates that type into a variable parameter. When the type library is saved, the variable parameter's associated ElemDesc's IDL flags are marked IDL_FIN or IDL_FOUT.

Often, ElemDesc IDL flags are not marked by IDL_FIN or IDL_FOUT when the type is preceded with a Pointer. Or, in the case of dispinterfaces, IDL flags are not typically used. In these cases, you may see a comment next to the variable identifier such as {IDL_None} or {IDL_In}. These comments are used when saving a type library to correctly mark the IDL flags.

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