problem canceling process

[softwareguy74]

Hi,

I asked a similar question recently and implemented the various suggestions that I received but, I ran into an unexpected problem which I did not explain in the first post..

Here's the situation:

I have a form which has 2 buttons. cmdStart and cmdCancel. As you can probably already guess, the cmdStart starts the process and cmdCancel cancels the process.

I used the following code behind the cmdCancel button:

    xVar = MsgBox("Are you sure you wish to cancel downloading?", _
        vbQuestion + vbYesNo)
    
    If xVar = 6 Then
        '-- cancel download operation
        If Winsock1.State <> sckClosed Then
            Winsock1.Close 'close socket if open
        End If
        Unload Me
    End If

However, the code behing cmdStart is "modular" in nature. For example:

cmdStart calls a sub which does some various processing, calls another function to get a value, takes that value and does a calculation, etc...

I beleive that the above CANCEL code would in fact work if the code behind cmdSend was not modular in nature. But, the fact is that I am using modular programming so the above cancel code raises various errors througout the various functions/subs depending on where the fucntion/sub was when the user hit the Cancel button. I do not want to put an error handling routine in each function/sub that cmdStart calls to handle the cancelling.. I'm sure there is a better way to handle "Cancelling" in modular programming..

Does anyone have any ideas on how to easily and "effeciently" cancel processing when you're dealing with modular programming?

Thanks,

Dan

[parksie]

The best way is exceptions, which will appear in the next version of VB (they've been in other languages for ages). Other than that, how about setting some global variable, then exiting up the call stack? (the call stack is the functions that have been called in reverse order, ie the current function is on top, it's caller is next, and so on)

[softwareguy74]

That sounds interesting.. I'd like to try it but don't know how.. How do you "exit up the call stack"? An example would be appreciated..

Dan

[parksie]

Something like this:

Dim iErrorCode As Integer
Sub RootSub()
    iErrorCode = 0 ' No error
    NextSub
    If iErrorCode <> 0 Then
        Debug.Print "Error " & iErrorCode & " encountered"
        Exit Sub
    End If

    ' Continue
End Sub
Sub NextSub()
    OtherSub
    If iErrorCode <> 0 Then
        Exit Sub
    End If
    DifferentSub
End Sub
Sub OtherSub
    iErrorCode = 1
End Sub
Sub DifferentSub
    Debug.Print "Hit DifferentSub"
End Sub