Is it possible - err.handler problem

[ermingut]

Look at this code:

On Error GoTo err_han
   Dim DataFile as Field
   Do Until recordset1.EOF
        strPath = DataFile
             Open strPath For Input As #1
lab1:    recordset1.MoveNext
   Loop
Exit Sub
err_han:
Select Case Err.Number
 Case Is = 53
        Label2.Caption = "No file to open"
        DoEvents
        GoTo lab1
 Case Else
      MsgBox Err.Number & " - " & Err.Description & " - " & Err.Source
End Select

On first execution of DO LOOP error handler traps err.number 53 (File ton found)- That OK!

On next execution (second step) error handler does not work and I get Run time error '53'. File not found!

Is this weird or what?

[TheSarlacc]

i had the same problem ages ago! it annoyed the crap outta me.

put an On Error goto err_han after the err_han: line

vb will produce error messages if an error occurs while inside an error handler subroutine! so u tell vb that u r not handling errors anymore, and if one happens, goto [label]. sort of like a trick

[ermingut]

If I tell VB not to handle errors it my code will create run time error very often. I use error handler to trap all kinds of errors and in error handler I have code that handles that error. This code can be quite complex.

So I can't tel VB not to handle error.

[TheSarlacc]

sorry i am not good at explainin code, just givin it! hehe lol
just do what i told ya and it will work

[Frans C]

Vb doesn't invoke the error handler if it thinks it is handling an error already. So an error inside the error handler will not be handled by this error handler.
This means you need to tell vb that error handling is finished, and you resume with normal code.
You do this with the Resume keyword.
Replace 'GoTo lab1' with 'Resume lab1' and all should work again.

[TheSarlacc]

took the words right out of my mouth

[honeybee]

Originally posted by Frans C
Vb doesn't invoke the error handler if it thinks it is handling an error already. So an error inside the error handler will not be handled by this error handler.
This means you need to tell vb that error handling is finished, and you resume with normal code.
You do this with the Resume keyword.
Replace 'GoTo lab1' with 'Resume lab1' and all should work again.

I tend to disagree with the former part of your opinion. I have some code in which I have created the error handler as a DLL. Every time there is an error, from my application I call the error object in my DLL. I had forgotten to create a new instance of this object in the first place. So the first time an error occured in my application, the control went inside the error handler, tried to invoke the error object in my DLL and since it had not been instantiated, fired another error, which was again trapped inside the same error handler.

So I think even if your error handler causes any errors, they will be trapped by the same error handling code.

And I agree with the later part, that you should use 'Resume ...' to resume control in the normal code.

.

[Frans C]

If I understood it right, the following thing happens:
If an error occurs in a procedures error handler, the first error handler up in the call stack is invoked. If there is no such error handler, a standard error message is displayed and the program is terminated.
The following test proves this:

Private Sub Command1_Click()
    Call CheckError1
End Sub

Private Sub CheckError1()
On Error GoTo HandleIt
    Call CheckError2
    Exit Sub
HandleIt:
    MsgBox "CheckError1"
End Sub

Private Sub CheckError2()
    Call CheckError3
End Sub

Private Sub CheckError3()
Dim x As Double
On Error GoTo HandleIt
    x = 1 / 0
    Exit Sub
HandleIt:
    MsgBox "CheckError3"
    x = 1 / 0
End Sub

The first error occurs in procedure CheckError3, the error handler is invoked, and the messagebox says "CheckError3". Next another error is generated inside the error handler. Because the error is invoked inside the error handler of CheckError3, its error handler is not invoked, instead the error handler of CheckError2 should be invoked, but this procedure doesn't have one. One step up in the call stack is procedure CheckError1, and this his an error handler. The next messagebox says CheckError1.

I rest my case.

[honeybee]

Yikes! I hate to say this, but

YOU ARE RIGHT!

Option Explicit

Private Sub Form_Activate()
On Error GoTo MyError
    Err.Raise 5
    Exit Sub

MyError:
    MsgBox Err.Description
    Err.Raise 13
End Sub

I shall seek solace in proving you right in fewer lines of code!

.

[Frans C]

But your example doesn't show that the calling sub's error handler is used.

[ermingut]

Thanks guys. I solved my problem with

resume lab1

code. But then I saw that my code isn't written as it should be so I rewrite it and doesn't need error handling in that part anymore.

But it was a good school of error handling!

Thanks!

[honeybee]

Originally posted by Frans C
But your example doesn't show that the calling sub's error handler is used.

If you try the example, the runtime error 5 is trapped in the error handler MyError. Then the error 13 is not trapped, and VB pops up its error dialog. This proves that the same error handler is not used to handle errors inside the error handling code.

According to my argument, even for error 13, the MyError code should have been invoked. But since it does not happen so, my argument is false.

.

[vbcoder]

The error you are encountering is due to the fact you haven't closed the initial file you were trying to read.
you opened a file within the loop but did not CLOSE it. The second pass of the loop is tryin to open another file
to the same file handle. If you are trying to open multiple sources you will need to change the File handle to a variable that is different for each one.

[ORIGINAL]
On Error GoTo err_han
Dim DataFile as Field
Do Until recordset1.EOF
strPath = DataFile
Open strPath For Input As #1
lab1: recordset1.MoveNext
Loop

[Option #1]
On Error GoTo err_han
Dim DataFile as Field
Do Until recordset1.EOF
strPath = DataFile
Open strPath For Input As #1
Close (#1)
lab1: recordset1.MoveNext
Loop

[Option #2]
[ORIGINAL]
On Error GoTo err_han
Dim DataFile as Field
Do Until recordset1.EOF
strPath = DataFile
fhInFile = freefile
Open strPath For Input As #(fhInFile)
lab1: recordset1.MoveNext
Loop


If you are trying to determine if a file exists then try this instead.

On Error GoTo err_han
Dim DataFile as Field
Do Until recordset1.EOF

strPath = DataFile

If len(dir(strpath)) > 0 then
' this is a valid file.
else
' this file does NOT exist.
end if

lab1: recordset1.MoveNext

Loop

[ermingut]

Actually I forgot to write in my sample code

close #1.

A did that somewhere in the proccess, so my filenumber #1 was "free" for new open file.

but any way VB should trap error for wrong file number but it didn't.

That was NOT my problem.

resume lab1:

solved my problem. But as I said I rewrote entire procedure so i don't need error handling anymore!

[KamiKazeKiwi3]

Simple. If you wanna stop the file not found error, tell VB to open another file, a dummy file, and then close it. Then inform the user if it's their fault.