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Displaying Data Values

So far, you have only been using Debug.Print to print simple text messages to yourself, but you can also use it to display data values. (Because some of your text messages have used string variables, perhaps that is obvious.) A few rules apply to data variables when they are displayed via Debug.Print. Most of these rules apply equally well to every other aspect of VB, so they are pretty straightforward and should not cause you any difficulty even if you don’t remember them.

The Immediate window is aware of any locale settings you have established for your system. Consequently, if you use Debug.Print to display numeric data, the values will be displayed with the appropriate decimal separator, and any keywords will appear in your chosen language. Date variables will be displayed in the short date format recognized by your system. Boolean values are displayed as either true or false. These are the same default behaviors you should see anywhere in VB.

If you are testing variables to see whether they contain values, remember that empty is not the same state as null. If the value of an empty variable is displayed, nothing is printed (not the word nothing, but literally nothing). If the variable is null, the word Null is printed in the Immediate window.

Here are some examples of how data may be output to the Immediate window:

LISTING 18.4
OUTPUT OF DATA TO THE IMMEDIATE WINDOW

Sub DebugPrintExamples()
‘ Display a decimal value
Dim s As Single
s = 3.14159
Debug.Print "The value of s is"; s
‘ Display a Boolean
Dim fMakesSenseToMe As Boolean
Debug.Print "The default value of a Boolean is ";
fMakesSenseToMe
‘ Display a date
Dim d As Date
d = Date
Debug.Print "Today is "; d
‘ Empty vs. Null
Dim var1 As Variant, var2 As Variant
Debug.Print "Before any assignment, a Variant is "; var1
Debug.Print "Can’t see that? Of course not; it really IS
empty!"
Debug.Print "OK, True or False. The statement ‘var1 is
Empty’ is "; IsEmpty(var1)
Debug.Print "and the statement ‘var1 is Null’ is ";
IsNull(var1)
‘ After an assignment, can var be reassigned a value of
Empty?
var1 = 1: var1 = Null
Debug.Print "Now, var1 is "; var1;
Debug.Print ", so the value of IsEmpty(var1) is ";
IsEmpty(var1)
Debug.Print "Not surprisingly, the statement ‘var1 is Null’
is "; IsNull(var1)
var1 = Empty
Debug.Print "A Variant can become Empty again by
assignment: "; IsEmpty(var1)
var1 = 1: var1 = var2
Debug.Print "or by being assigned the value of another
empty Variant: "; IsEmpty(var1)
End Sub

It used to be that after a Variant had been assigned a value, it could become empty again only by being assigned the value of another empty Variant. Now you can just reassign the value empty to the variable.


  

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