Overview of Variants

Variants were first introduced in version 2 of Visual Basic as a flexible data type that could hold each of the simple data types. The Variant data type was extended substantially with version 4 to include Byte, Boolean, Error, Objects, and Arrays, and a little further with version 5 to include the Decimal data type. The Decimal data type was the first data type that was not available as a "first class" data type—it is available only within a Variant—and you cannot directly declare a variable as a Decimal.

In Visual Basic 6, UDTs have been added to the list, effectively completing the set. Now a Variant can be assigned any variable or constant, whatever the type.

A variety of functions convert to these subtypes and test for these subtypes. Table 4-1 shows the development of the Variant data type through the versions of Visual Basic, along with the matching functions.

Table 4-1 The Evolution of Variants

Type	Visual Basic Name	Visual Basic Version	Convert Function	Test Function
0	Empty	2	= Empty	IsEmpty
1	Null	2	= Null	IsNull
2	Integer	2	CInt	IsNumeric*
3	Long	2	CLng	IsNumeric
4	Single	2	CSng	IsNumeric
5	Double	2	CDbl	IsNumeric
6	Currency	2	CCur	IsNumeric
7	Date	2	CVDate/CDate	IsDate
8	String	2	CStr
9	Object	4		IsObject
10	Error	4	CVErr	IsError
11	Boolean	4	CBool
12	Variant	4	CVar
13	Data Object	4
14	Decimal	5	CDec	IsNumeric
17	Byte	4	CByte
36	UDT	6
8192	Array	4	Array	IsArray
16384	ByRef	Never?

*Strictly speaking, IsNumeric tests to see if a variable can be converted to a numeric value, and is not simply reporting on a Variant's subtype.