[Gambas-user] Finally/Catch and Return: How is that meant to be used?
benoit.minisini at gambas-basic.org
Thu Sep 14 16:30:19 CEST 2023
Le 14/09/2023 à 16:03, Martin Fischer a écrit :
> Hi all,
> I think I don't understand the approach to error handling gambas has
> Let's take a simple, very common problem: a function that shall return
> the id (int) of something. To get this id, a looooong and very
> complicated sequence of steps have to be taken. This involves the
> allocation of resources that have to be cleaned up in any case. All
> kinds of errors could happen on the way (errors might get risen).
> Here is pseudocode for this:
> Public Function getComplicatedId() As Integer
> Dim result As Integer
> ' do some very complicated stuff
> ' resources are allocated on the way. E.g. heap Alloc
> Return result
> ' clean up resources here
> ' do some logging here
> Error.Raise("Can't handle this!")
> The first problem with this code is that the "Return result" causes the
> Finally block to be skipped.
> Moving the "Return result" as last statement into the Finally block does
> work but prevents the Catch block to be executed in case of an error. Bad.
> I'm sure that there is a way to handle cleanup and errors in a clean
> manner (I mean: without Gotos and Labels). I just can't see how to do it
> with Return, Finally and Catch...
> Does anyone have an explanation or example or reference to a
> sample/documentation for this problem?
> Martin Fischer
The only way to deal with that problem I see is the following:
Public Function getComplicatedId() As Integer
Dim result As Integer
Dim bReturn As Boolean
' do some very complicated stuff
' resources are allocated on the way. E.g. heap Alloc
bReturn = True
' clean up resources here
if bReturn Then Return result
' do some logging here
Error.Raise("Can't handle this!")
The interpreter misses a flag local to the function that allows to tell
that Finally was reached without raising an error.
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