Intrinsic Constants

Intrinsic constants are ones that are automatically defined by Access or VBA. You can find a full list of these in the Access help file, under the Visual Basic Language Reference section.

For example, earlier in the chapter we used the VarType() function to determine the type of a variant. If you wanted to test a variant to see whether it contained a string you could do this:

   If VarType(varAnyThing) = 8 Then   

However, this has the immediate disadvantage in that you must know what the value 8 means. Luckily there is a set of intrinsic constants just for this purpose. Let's have another look at the table:

Value	Variant type	Constant
	Empty ( uninitialized )	vbEmpty
1	Null (no valid data)	vbNull
2	Integer	vbInteger
3	Long Integer	vbLong
4	Single	vbSingle
5	Double	vbDouble
6	Currency	vbCurrency
7	Date	vbDate
8	String	vbString
9	Object	vbObject
10	Error value	vbError
11	Boolean	vbBoolean
12	Variant (only used with arrays of variants)	vbVariant
13	Data access object	vbDataObject
14	Decimal value	vbDecimal
17	Byte	vbByte
36	User Defined Type	vbUserDefinedType
8192	Array	vbArray

Now our code becomes much more readable:

   If VarType(varAnyThing) = vbString Then   

You'll see plenty of uses of intrinsic and user-defined constants as we go through the book.