Although most of the uses to which you have put the Immediate window so far
have required that a program be suspended in Break mode, you can do some things
with the Immediate window that don’t require a program at all. If you want
to execute a command or run a procedure that you have written, you can just type
the command or procedure name (along with any necessary parameters) into the Immediate
window, and then press the Enter key.
Assume, for example, that you want to delete a file using the
Kill statement, but you aren’t sure what will happen if you put the
command in your program and the file doesn’t exist. You can enter the command
in the Immediate window twice in succession to see what it will do, as shown in
Figure 18.19.
FIGURE 18.19 Deleting a file with the Kill statement.
As you can see, nothing special happens in the Immediate window to indicate
that the command succeeded. If you try to execute the Kill
command again, however, you will generate a runtime error (#53: File not
found) because the file was successfully deleted the first time.
Perhaps it would be nice to have a more informative way to delete a file. There
is no way to modify the built-in Kill statement to
provide extra information, but you can write your own file deletion function that
does. Here is one that uses the Kill command to do
its dirty work, but that uses the Immediate window to display its status along
the way. Most important, the new function also provides a return value to indicate
whether it succeeded:
LISTING 18.5
A FILE DELETION FUNCTION
Function Delete(sFilename As String) As Boolean
‘ use the return value in the calling function rather than
trap the error here
On Error Resume Next
Dim fReturn As Boolean
#Const DEBUGGING = True
‘ see if the file exists to delete
If Dir(sFilename) <> "" Then fReturn = True
#If DEBUGGING Then
Debug.Print "File exists = "; fReturn
#End If
If fReturn Then
‘ file exists, so kill it
Kill sFilename
‘ if couldn’t delete, set return value
If Dir(sFilename) <> "" Then fReturn = False
#If DEBUGGING Then
Debug.Print "File deleted = "; fReturn
#End If
End If
Delete = fReturn
End Function
If you run this function twice in succession, the Immediate window looks like
Figure 18.20.
FIGURE 18.20 Results of the Delete function displayed in the Immediate window.
The Delete function is more informative than the
Kill statement at debug time because it uses Debug.Print
to keep you posted about its progress. Aside from the debugging output,
Delete also gives you more to work with in your program. Because it provides a
Boolean return value, you can test for the success of the file deletion and take
appropriate measures in your program.
Because Delete is a function, it also enables you to display useful output
in the Immediate window without sprinkling Debug.Print statements
throughout its body. If you remove the "#Const DEBUGGING
= True" line and run Delete from the Immediate window, you can use
the Debug.Print statement to display its return value,
as shown in Figure 18.21.
FIGURE 18.21 Results of the Delete function displayed
in the Immediate window with the Debug.Print method.
This gives you two ways to run a procedure from the Immediate window: with
or without prefacing it with Debug.Print. If you just
want to execute a procedure and disregard its return value (if it has one), don’t
use the Print method. If you want to display the return
value of a function, preface it with a leading question mark to invoke
Debug.Print.
NOTE - Functions Versus Subs in the Immediate Window:
You can treat a function like a sub in the Immediate window, but you
can’t treat a sub like a function. If you inadvertently put a leading question
mark in front of a sub that you try to run in the Immediate window, you will get
this error message: Compile error: expected function
or variable
