Coding Convention Questions #1 (On Error Goto 0 before End Sub)

I'm mainly self taught at VBA so I make notes on various coding conventions/practices etc. that I pick up from books & websites.
I've noticed that some of these conventions conflict with one another or don't appear to have a logical rationale upon closer inspection.
So I figure that I would pose some of these to the Forum so I can be taught by others far more skilled and experienced than I.

Here's the first one:

I've come across a coding convention where you place

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before the procedure exit/end.

I started to take this practice up but when I recently questioned the logic for doing so, I couldn't work out why you would do this.

Error Handling takes place at a procedure level. When a procedure ends, the error handling for that procedure resets so why would you need to reset it?

Or am I overlooking something big?

Correct me if my understanding is wrong.

1. Error handling takes place at a procedure level.
2. If a procedure doesn't contain error handling, it throws back to the calling procedure before it.
3. This repeats until it reaches a calling procedure that does have error handling - and then uses that.
4. If the entire chain doesn't contain error handling or if the procedure was 'stand alone' and didn't contain error handling then you get the standard VBA Error Msgbox.

If I have the above correct then why would you want/need to place

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before exiting a procedure?

It resets any current error.

And disables the enabled error handler for that procedure.

But is this necessary if the next line is Exit/End Sub?

Hello mc84excel,

If your error handler is not jumping back to a particular line in the procedure and will exit the procedure when finished, the On Error GoTo 0 is redundant and not needed.

Originally Posted by Leith Ross

If your error handler is not jumping back to a particular line in the procedure and will exit the procedure when finished, the On Error GoTo 0 is redundant and not needed.

Thanks. That's what I suspected.


On a side note: If the error handler DOES jump back to the procedure, (rough example below)

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then I take it I would need an

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before

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in the ErrHandler? (Assuming I want to keep using the same error handler for that procedure)

Hello mc84excel,,

You're welcome.

Hello mc84excel,

You can use either Err.Clear or On Error GoTo 0 to clear the error. You only need to clear the error if you intended to trap the error again during code execution. There may be times were you expect a certain error to occur and it can be ignored. In this case, you can resume without clearing the error.

Thanks again.


(Since I want to reuse the error handler in the procedure, I will use

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rather than

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)

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Hello mc84excel,

You're welcome.

@ shg. If I get what you are saying - Errors are not automatically cleared at procedure exit/end (although the error handler itself is cleared at procedure exit/end). If there was a calling procedure to the procedure that encountered the error, the error number will 'throw back' up the call stack. But if you had

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before the procedure exit/end, then not only is the procedure err handler disabled (which isn't necessary as we are leaving the procedure), it also resets the error to 0. But why do we want to do this?

If you are of the "I prefer error throw back to top level procedure" school (which I'm not) then using this before the exit point erases the error so the top level will never capture what went wrong.

If you are of the "handle the error in the procedure that encounters it" then we would have already run our ErrHandler code.

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I wasn't expressing an opinion, just answering the question.