Miscellaneous Functions and Statements
We’ll conclude our discussion of Access VBA functions and statements by examining a hodgepodge of language constructs that perform such tasks as evaluating objects or variables, evaluating an expression, and altering program flow based on an expression’s values.
The Is Functions
VBA has several Is functions that return Boolean values indicating
whether a certain condition holds. We have already discussed the
IsMissing
function in connection with optional
arguments. Here are some additional Is functions.
The IsDate function
This function indicates whether an expression can be converted to a date. For instance, the code:
Dim x As String x = "1/1/45" Debug.Print IsDate(x)
will print True
to the Immediate window.
The IsEmpty function
This function indicates whether a variable has been initialized. For example, the code:
Dim x As Variant If IsEmpty(x) Then . . .
tests whether the variable x
is empty.
The IsNull function
This function is used to test whether
a variable or field is Null
(that is, contains no
data). Note that code such as:
If var = Null Then
will always return False
because most expressions
that involve Null
automatically return
Null
. The proper way to determine if the variable
var
is Null
is to
write:
If IsNull(var) Then
Here is a typical scenario:
Dim rs As Recordset Dim s As String Set rs = CurrentDb.OpenRecordset("Names") rs.MoveFirst If Not IsNull(rs!LastName) Then s = rs!LastName . . . End If
The IsNumeric function
This function indicates ...
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