On Error Goto -1 On Error Goto 0 

On Error Goto -1 

Err.Clear On Error Goto MyErrorHandlerLabel 

Option Compare Database Option Explicit Dim RememberErrNumber As Long Dim RememberErrDescription As String Dim RememberErrSource As String Dim RememberErrLine As Integer Private Sub RememberThenClearTheErrorObject() On Error Resume Next " For demo purposes Debug.Print "ERROR RAISED" Debug.Print Err.Number Debug.Print Err.Description Debug.Print Err.Source Debug.Print " " " This function has to be declared in the same scope as the variables it refers to RememberErrNumber = Err.Number RememberErrDescription = Err.Description RememberErrSource = Err.Source RememberErrLine = Erl() " Note that the next line will reset the error object to 0, the variables above are used to remember the values " so that the same error can be re-raised Err.Clear " Err.Clear is used to clear the raised exception and set the err object to nothing (ie err.number to 0) " If Err.Clear has not be used, then the next "On Error GoTo ALabel" that is used in this or the procedure that called it " will actually NOT pass execution to the ALabel: label BUT the error is paseed to the procedure that called this procedure. " Using Err.Clear (or "On Error GoTo -1 ") gets around this and facilitates the whole TRY CATCH block scenario I am using there. " For demo purposes Debug.Print "ERROR RAISED is now 0 " Debug.Print Err.Number Debug.Print Err.Description Debug.Print Err.Source Debug.Print " " " For demo purposes Debug.Print "REMEMBERED AS" Debug.Print RememberErrNumber Debug.Print RememberErrDescription Debug.Print RememberErrSource Debug.Print " " End Sub Private Sub ClearRememberedErrorObjectValues() " This function has to be declared in the same scope as the variables it refers to RememberErrNumber = 0 RememberErrDescription = "" RememberErrSource = "" RememberErrLine = 0 End Sub Sub ExampleOfTryCatchBlockInVBA() On Error GoTo HandleError " ----------------------------------------------------- " SubProcedure1 has the example of a multiple line TRY block with a block of code executed in the event of an error SubProcedure1 Exit Sub HandleError: Select Case Err.Number Case 0 " This shold never happen as this code is an error handler! " However if it does still allow the Err.raise to execute below. (In this case Err.raise will fail " and itself will raise an error "Invalid procedure call or argument" indicating that 0 cannot be used to raise and error! Case 111111 " You might want to do special error handling for some predicted error numbers " perhaps resulting in a exit sub with no error or " perhaps using the Err.raise below Case Else " Just the Err.raise below is used for all other errors End Select " " I include the procedure ManageErrSource as an exmple of how Err.Source can be used to maintain a call stack of procedure names " and store the name of the procedure that FIRST raised the error. " Err.Raise Err.Number _ , ManageErrSource("MyModuleName", Err.Source, Erl(), "tsub1_RaisesProcedureNotFoundError") _ , Err.Number & "-" & Err.Description " Note the next line never gets excuted, but I like to have resume in the code for when I am debugging. " (When a break is active, by moving the next executable line onto it, and using step over, it moves the exection point to the line that actually raised the error) Resume End Sub Sub SubProcedure1() " ----------------------------------------------------- " Example of a multiple line TRY block with a Case statement used to CATCH the error " " It is sometimes better to NOT use this technique but to put the code in it"s own procedure " (ie I refer to the code below that is surrounded by the tag #OWNSUB) . " However,sometimes using this technique makes code more readable or simpler! " Dim i As Integer " This line puts in place the defualt error handler found at the very foot of the procedure On Error GoTo HandleError " " Perhaps lots of statements and code here " " First an example with comments " ----------------------------------------------------- " TRY BLOCK START " This next line causes execution to "jump" to the "catch" block in the event an error is detected. On Error GoTo CatchBlock1_Start " #OWNSUB tsub_WillNotRaiseError_JustPrintsOk If vbYes = MsgBox("1. Do you want to raise an error in the try block? - (PRESS CTRL+BREAK now then choose YES, try no later.)", vbYesNo) Then i = 100 / 0 End If " " Perhaps lots of statements and code here " " #OWNSUB " TRY BLOCK END " ----------------------------------------------------- " ----------------------------------------------------- " CATCH BLOCK START CatchBlock1_Start: If Err.Number = 0 Then On Error GoTo HandleError " Re-instates the procedure"s generic error handler " This is also done later, but I think putting it here reduces the likelyhood of a coder accidentally removing it. Else " WARNING: BE VERY CAREFUL with any code that is written here as " the "On Error GoTo CatchBlock1_Start" is still in effect and therefore any errors that get raised could goto this label " and cause and infinite loop. " NOTE that a replacement "On Error Goto" cannot be executed until Err.clear is used, otherwise the "On Error Goto" " will itself raise and error. " THEREFORE KEEP THE CODE HERE VERY SIMPLE! " RememberThenClearTheErrorObject should be the only code executed and this called procedure must be tight! " This saves the details of the error in variables so that the "On Error GoTo HandleError" can be used " to determine how the next Err.Raise used below is handled (and also how any unexpected implicitly raised errors are handled) RememberThenClearTheErrorObject On Error GoTo HandleError "#THISLINE# If vbYes = MsgBox("2. Do you want to raise an error in the erro handler? - (PRESS CTRL+BREAK now then try both YES and NO )", vbYesNo) Then i = 100 / 0 End If Select Case RememberErrNumber Case 0: " No Error, do Nothing Case 2517 Debug.Print "The coder has decided to just give a Warning: Procedure not found " & Err.Number & " - " & Err.Description ClearRememberedErrorObjectValues " Not essential, but might save confusion if coding errors are made Case Else " An unexepected error or perhaps an (user) error that needs re-raising occurred and should to be re-raised " NOTE this is giving an example of what woudl happen if the CatchBlock1_ErrorElse is not used below If vbYes = MsgBox("3. Do you want to raise an error in the ELSE error handler? CatchBlock1_ErrorElse *HAS NOT* been used? - (PRESS CTRL+BREAK now then try both YES and NO )", vbYesNo) Then i = 100 / 0 End If On Error GoTo CatchBlock1_ErrorElse " SOME COMPLEX ERROR HANDLING CODE - typically error logging, email, text file, messages etc.. " Because the error objects values have been stored in variables, you can use " code here that might itself raise an error and CHANGE the values of the error object. " You might want to surround the code with the commented out CatchBlock1_ErrorElse lines " to ignore these errors and raise the remembered error. (or if calling a error handling module " just use on error resume next). " Without the CatchBlock1_ErrorElse lines any error raised in this "complex code" will be handled by the " active error handler which was set by the "On Error GoTo HandleError" tagged as "#THISLINE#" above. If vbYes = MsgBox("4. Do you want to raise an error in the ELSE error handler when CatchBlock1_ErrorElse HAS been used? - (PRESS CTRL+BREAK now then try both YES and NO )", vbYesNo) Then i = 100 / 0 End If CatchBlock1_ErrorElse: On Error GoTo HandleError " This line must be preceeded by an new "On error goto" for obvious reasons Err.Raise RememberErrNumber, RememberErrSource, RememberErrDescription End Select On Error GoTo HandleError End If " CATCH BLOCK END " ----------------------------------------------------- On Error GoTo HandleError " Unnecessary but used to delimt the catch block " " lots of code here perhaps " " ----------------------------------------------------- " Example 2 " " In this example goto statements are used instead of the IF statement used in example 1 " and no explanitory comments are given (so you can see how simple it can look) " " ----------------------------------------------------- " TRY BLOCK START On Error GoTo CatchBlock2_Start tsub_WillNotRaiseError_JustPrintsOk If vbYes = MsgBox("Do you want to raise an error? - (PRESS CTRL+BREAK now then choose YES)", vbYesNo) Then i = 100 / 0 End If " " Perhaps lots of statements and code here " " TRY BLOCK END " ----------------------------------------------------- GoTo CatchBlock2_End: CatchBlock2_Start: RememberThenClearTheErrorObject On Error GoTo HandleError Select Case RememberErrNumber Case 0: " No Error, do Nothing Case 2517 Debug.Print "The coder has decided to just give a Warning: Procedure not found " & Err.Number & " - " & Err.Description ClearRememberedErrorObjectValues " Not essential, but might save confusion if coding errors are made Case Else " An unexepected error or perhaps an (user) error that needs re-raising occurred and should to be re-raised " In this case the unexpecetd erro will be handled by teh code that called this procedure " This line must be preceeded by an new "On error goto" for obvious reasons Err.Raise RememberErrNumber, RememberErrSource, RememberErrDescription End Select On Error GoTo HandleError End If CatchBlock2_End: " CATCH BLOCK END " ----------------------------------------------------- On Error GoTo HandleError " Unnecessary but used to delimt the catch block " " Here you could add lots of lines of vba statements that use the generic error handling that is after the HandleError: label " " " " You could of course, alway add more TRY CATCH blocks like the above " " Exit Sub HandleError: Select Case Err.Number Case 0 " This shold never happen as this code isan error handler! " However if it does still allow the Err.raise to execute below. (In this case Err.raise will fail " and itself will raise an error "Invalid procedure call or argument" indicating that 0 cannot be used to raise and error! Case 111111 " You might watch to do special error handling for some predicted error numbers " perhaps exit sub " Perhaps using the Err.raise below End Select " ie Otherwise " " Note that I use the Err.Source to maintain a call stack of procedure names " Err.Raise Err.Number _ , ManageErrSource("MyModuleName", Err.Source, Erl(), "tsub1_RaisesProcedureNotFoundError") _ , Err.Number & "-" & Err.Description " Note the next line never gets excuted, but I like to have resume in the code for when I am debugging. " (By moving the next executable line onto it, and using step over, it moves the exection point to the line that actually raised the error) Resume End Sub Sub tsub_WillNotRaiseError_JustPrintsOk() Static i As Integer i = i + 1 Debug.Print "OK " & i End Sub Public Function ManageErrSource(MyClassName As String, ErrSource As String, ErrLine As Integer, ProcedureName As String) As String " This function would normally be in a global error handling module " On Error GoTo err_ManageErrSource Const cnstblnRecordCallStack As Boolean = True Select Case ErrSource Case Application.VBE.ActiveVBProject.Name " Err.Source is set to this value when a VB statement raises and error. eg In Access by defualt it is set to "Database" ManageErrSource = Application.VBE.ActiveVBProject.Name & " " & MyClassName & "." & ProcedureName & ":" & ErrLine Case "" " When writing code ouside of the error handling code, the coder can raise an error explicitly, often using a user error number. " ie by using err.raise MyUserErrorNumber, "", "My Error descirption". " The error raised by the coder will be handled by an error handler (typically at the foot of a procedure where it was raised), and " it is this handler that calls the ManageErrSource function changing the Err.Source from "" to a meaningful value. ManageErrSource = Application.VBE.ActiveVBProject.Name & " " & MyClassName & "." & ProcedureName & ":" & ErrLine Case Else " This code is executed when ManageErrSource has already been called. The Err.Source will already have been set to hold the " Details of where the error occurred. " This option can be used to show the call stack, ie the names of the procdures that resulted in the prcedure with the error being called. If cnstblnRecordCallStack Then If InStr(1, ErrSource, ";") = 0 Then ManageErrSource = ErrSource & ":: Called By: " End If ManageErrSource = ErrSource & ";" & ProcedureName & ":" & ErrLine Else ManageErrSource = ErrSource End If End Select Exit Function err_ManageErrSource: Err.Raise Err.Number, "MyModuleName.err_ManageErrSource", Err.Description Resume End Function 

Problemet er at kjøretidsfeil i VBA er ikke unntak , og feilhåndtering i VBA har veldig lite til felles med unntakshåndtering.

RememberErrLine = Erl() 

Erl -funksjonen er et skjult medlem av VBA.Information -modulen av en grunn – den returnerer 0 med mindre feilen oppstod på en nummerert linje. Og hvis du bruker linjenumre i VBA, har du bodd i en hule i 25 år og bruker sannsynligvis GoSub uttalelser i stedet for å skrive prosedyrer. Linjenumre støttes av arv / bakoverkompatibilitetsmessige grunner fordi koden skrevet i 1980ene krevde dem.

Jeg liker hvordan du sa det selv:

" THEREFORE KEEP THE CODE HERE VERY SIMPLE! 

..men hvorfor gjaldt ikke det for resten av koden? Ingen krenkelse, men dette er spaghettilogikk, skrevet i prosedyrer som tydelig og skamløst bryter Enkelt ansvarsprinsipp . Ingen SRP-kompatibel kode trenger noen gang to av slike » prøvefangst » blokker.

Dette lukter:

Case 0: " No Error, do Nothing 

Det betyr en av to ting: enten har du feilhåndteringskode som kjører i ikke-feilkontekster, eller du har død kode som skal slettes.

Dette lukter reeks :

GoTo CatchBlock2_End: CatchBlock2_Start: 

For det første, ac olon (:) som ikke spesifiserer en linjeetikett , er en instruksjonsskiller .Det viser seg at en ny linje også er en » instruksjonsskiller «, så kolon på slutten av GoTo CatchBlock2_End er helt ubrukelig og forvirrende, spesielt gitt innrykkingsnivået til GoTo-setningen .

Apropos GoTo …

Neil Stephenson synes det er søtt å gi etikettene hans navnet» dengo «

Jeg liker ikke hvordan jeg trenger å hoppe mellom etikettene for å følge koden. IMO det er rotete og unødvendig spaghettifisert.

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Fin, smartypants . Så hvordan håndterer man feil i VBA da?

1. Skriv ren kode med det første.

Følg de beste fremgangsmåtene, og skriv små prosedyrer som gjør en ting, og gjør det bra.

2. Skriv objektorientert kode.

Abstraksjon og innkapsling er to av de fire søylene i OOP , og de «støttes fullt ut i VBA. Polymorfisme er også noe av et alternativ; bare riktig arv er utelukket, men det hindrer ikke en i å abstrahere begreper i klassemoduler og instansering av spesialiserte objekter.

Prosedyrekode skrevet i standardmoduler (.bas) bør være små, små offentlige metoder (makro » kroker «) som skaper objektene som kreves for å kjøre funksjonaliteten.

Så hvordan forholder det seg eksternt til riktig feilhåndtering?

3. Ta imot idiomatisk feilhåndtering, ikke kjemp mot den.

Gitt kode som følger de ovennevnte punktene, er det ingen grunn til ikke å implementere feilhåndtering den idiomatiske VBA-veien.

Public Sub DoSomething() On Error GoTo CleanFail "method body CleanExit: "cleanup code goes here. runs regardless of error state. Exit Sub CleanFail: "handle runtime error(s) here. "Raise Err.Number ""rethrow" / "bubble up" Resume CleanExit Resume "for debugging - break above and jump to the error-raising statement End Sub 

Dette mønsteret er analogt med en » try-catch-finally » på følgende måte:

• Kroppen er » prøv » del, som gjør hva metodenavnet sier og ingenting mer
• CleanFail er » fanger » del, som bare kjører hvis det oppstår en feil
• CleanExit er » til slutt » del, som kjører uansett om en feil ble reist eller ikke … med mindre du «re-kaster» . Men hvis du trenger å boble opp en feil for at ringekoden skal kunne håndteres, bør du ikke ha mye opprydding c ode å utføre, og du burde ha en veldig veldig god grunn til å gjøre det.

Hvis feilrutinen din kan føre til en feil, følger du ikke SRP. For eksempel er det å skrive til en loggfil en egen bekymring, som skal trekkes ut i noe Logger objekt som lever for å håndtere loggproblemer, og avslører metoder som håndterer sine egne feil . Feilhåndtering av underrutinkode bør være triviell.

Kommentarer

• Takk @mat ‘ selvtilfreds for at du tok tiden for å legge til kommentarer som virkelig hjalp meg ‘ opp for voldelig, men humoristisk kritikk. Jeg ‘ har gjennomgått koden min, og jeg ‘ gleder meg over å kunne si at de aller fleste følger de rektorene du skisserer. Forklaringen din var nyttig, og den fikk meg til å reflektere og innse at jeg ikke ‘ ikke satte pris på at VB og SQL Server TRY CATCH-utsagn bare brukes en gang i hver prosedyre (jeg trodde de var en betyr å ikke trenge å trekke ut kode for å gjøre den mer lesbar). Hvis du har lyst til å legge til flere kommentarer om ManageErrSource-prosedyren I ‘ m alle ører …
• @HarveyFrench I ‘ vil legge til litt til når jeg får en sjanse – hadde ikke ‘ t sett på denne 😉 referanse og bruk av VBIDE API krever spesielle sikkerhetsinnstillinger, noe som ikke er kult. Jeg ‘ har kommet til å bruke TypeName(Me) som kilde for tilpassede feil i klassemoduler, og den eneste måten en feil kan vite hvilken prosedyre det skjedde i, er å hardkode prosedyrenavnet til en lokal const, ideelt sett ikke så langt fra metoden ‘ s signatur. Jeg liker ideen om samtalestakler, men en ulempe er at du må » konsekvent skyve » og » pop » når du går inn / avslutter en prosedyre, ellers blir det løgn.
• Koden jeg mottok fra fmsinc.com kommer mye rundt av problemene jeg ‘ har hatt.Jeg ‘ Jeg setter pris på din mening. Se her codereview.stackexchange.com/questions/94498/… Jeg setter pris på tiden din da dette driver meg nøtter.

Lytt til Mat «sMug , men han dekket ikke situasjonen der du faktisk vet hvordan du kan komme deg etter en feil. For fullstendighet, vil jeg dekke det.

La oss se på hvordan vi ville gjort noe slikt i VB.Net først.

Try foo = SomeMethodLikelyToThrowAnException Catch e As SomeException foo = someDefaultValue End Try " some more code 

Den idiomatiske måten å gjøre dette på i VB6 er å ResumeNext. Skriv dette ned fordi det er bare gang jeg noen gang vil si det rett til ResumeNext.

On Error Goto ErrHandler foo = SomeMethodLikelyToRaiseAnError " some more code CleanExit: " clean up resources Exit Sub ErrHandler: If Err.Number = ConstantValueForErrorWeExpected Then foo = someDefaultValue Resume Next End If Resume CleanExit "or re-raise error Exit Sub 

Den alternative måten er å integrere denne logikken, som jeg synes er litt renere og nærmere Try...Catch idiomet, men det kan bli stygt raskt hvis det misbrukes.

On Error Resume Next foo = SomeMethodLikelyToRaiseAnError If Err.Number = ConstantValueForErrorWeExpected Then foo = someDefaultValue End If On Error Goto 0 

Enten er idiomatisk måte å håndtere forventede feil på, men hva du enn gjør. Ikke bry deg med Resume Next til du helt forstår hva det gjør og når det er passende . (Mer en advarsel til fremtidige lesere enn til deg. Du ser ut til å forstå grundig feilhåndtering i VB6. Kanskje litt for bra for ditt eget beste.)

Kommentarer

• Takk @RubberDuck for nyttige kommentarer. Å være ærlig, finner jeg meg selv ved å bruke » Ved feil fortsette neste » før ganske mange prosedyreanrop avte r som det vanligvis er et SELECT CASE som svarer på eventuelle feil. Den store feilen jeg er klar over er at jeg tar opp et brukerdefinert unntak i underprosedyren for å markere situasjoner som oppstår (som brukeren som ber om å avbryte behandlingen). Jeg tynner at jeg skal bruke funksjoner mer. Dette er en indikasjon på at min generelle kodestruktur er » ikke ideell » / dårlig, og jeg tror og jeg må ta tak i dette. Takk.
• Du ‘ har slått på et flott punkt @HarveyFrench. Unntak er for eksepsjonell oppførsel, ikke kontroll av flyt. Velkommen til CR.
• Jeg ‘ ville være veldig interessert i dine meninger om dette SO-spørsmålet: stackoverflow. no / spørsmål / 31007009 / …
• Koden jeg mottok fra fmsinc.com kommer rundt mange av problemene jeg ‘ har hatt det. Jeg ‘ Jeg setter pris på din mening. Se her codereview.stackexchange.com/questions/94498/…

Dette svaret er ment å forenkle Try / Catch-mønsteret for å være lett forståelig.

Dette er ikke veldig forskjellig fra vanlig innebygd feilhåndtering bortsett fra at den kan hoppe over flere linjer samtidig, håndtere en feil og deretter gjenoppta regelmessig kjøring. Dette er et veldig rent strukturert mønster for å håndtere en feil. Strømmen beveger seg veldig rent fra topp til bunn; ingen spaghettikode her.

Tradisjonelt sett er feilbehandleren plassert nederst. Men Try / Catch-konstruksjonen er så elegant. Det er en veldig strukturert måte å håndtere feil på og er veldig enkelt å følge. Dette mønsteret prøver å gjengi det på en veldig ren, kortfattet måte. Strømmen er veldig jevn og hopper ikke fra sted til sted.

Sub InLineErrorHandling() "code without error handling BeginTry1: "activate inline error handler On Error GoTo ErrHandler1 "code block that may result in an error Dim a As String: a = "Abc" Dim c As Integer: c = a "type mismatch ErrHandler1: "handle the error If Err.Number <> 0 Then "the error handler is now active Debug.Print (Err.Description) End If "disable previous error handler (VERY IMPORTANT) On Error GoTo 0 "exit the error handler Resume EndTry1 EndTry1: "more code with or without error handling End Sub 

Kilder:

• Pearson feilhåndtering i VBA
• Slik: Håndter kjøretidsfeil i VBA
• Riktig håndtering Feil i VBA (Excel)
• Min egen: Hvordan gjøre en feilhåndteringsblokk som Try / Catch

Korrekt styrt fungerer dette ganske pent. Det er et veldig rent flytende mønster som kan reproduseres hvor som helst det er behov.

Kommentarer

• @D_Bester, takk for koblingene og det enkle eksemplet. Jeg ‘ lærer fremdeles og fant tilbakemeldingene dine nyttige, men du må legge til en » Ved feil Gikk 0 » etter » på feil goto -1 «. Også etter refleksjon synes jeg det er bedre å bruke Err.Clear i stedet for » On Error Goto -1 » da det tydeligere viser hva skjer. Jeg ‘ Jeg finner hele denne feilhåndteringen i VBA litt svart.
• @D_Bester. Ved refleksjon er kodingen din bra hvis alt du vil gi brukeren en melding når en feil oppstår, men hva om du vil øke feilen på nytt? Noe som vil være et veldig vanlig scenario. Ta i betraktning.Hvis du kode forsøkte å slå opp en kunde ‘ detaljer, og den kunne ikke ‘ ikke få dem av en uventet grunn. Du må heve feilen på nytt og la koden som bruker koden din for å slå opp bestemme hva du skal gjøre.
• @HarveyFrench Hvis du vil øke feilen, bruk bare ‘ Err.Raise ‘. Ikke noe problem der forutsatt at koden er strukturert godt og feilhåndtering er aktivert i ringekoden.
• @HarveyFrench Err.Clear og On Error Goto -1 er IKKE ekvivalente. Se stackoverflow.com/a/30994055/2559297
• Du ‘ har rett i at de har ikke det samme beklager. Men jeg tror koden over fortsatt trenger On Error GoTo -1 erstattet med Err.Clear ellers » ‘ mer kode uten feilhåndtering » hopper til ErrHandler1 hvis det oppstår en feil.

Når det gjelder «CleanExit» og «Endelig» -emnet.

Mats s Mug wrote:

CleanExit er » til slutt » del, som kjører uavhengig av om det ble reist en feil eller ikke … med mindre du kaster om.

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En slik situasjon kan forekomme for eksempel i denne prosedyrekoden:

Prosedyremetode

Public Sub DoSomething() On Error GoTo CleanFail " Open any resource " Use the resource CleanExit: " Close/cleanup the resource Exit Sub CleanFail: Raise Err.Number Resume CleanExit End Sub 

Problem her : Hvis det oppstår feil i metodekroppen som må repareres i CleanFail, blir ikke CleanExit utført en t alt og dermed kan ikke ressursen lukkes ordentlig.

Jo, du kan lukke ressursen også i selve feilbehandleren, men det kan føre til at du har flere kodefragmenter der ressurshåndtering vil være / har skal gjøres.

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Mitt forslag er å bruke et egendefinert objekt for hver ressursbindende nødvendighet:

AnyResourceBindingClass

Private Sub Class_Initialize() "Or even use Mats "Create method" approach here instead. "Open/acquire the resource here End Sub Private Sub Class_Terminate() On Error GoTo CleanFail "Close/clean up the resource here properly CleanExit: Exit Sub CleanFail: MsgBox Err.Source & " : " & Err.Number & " : " & Err.Description Resume CleanExit End Sub Public Sub UseResource() "Do something with the resource End Sub 

Objektorientert tilnærming

Public Sub DoSomething() On Error GoTo CleanFail " Use custom object which acquires the resource With New AnyResourceBindingClass .UseResource End With CleanExit: Exit Sub CleanFail: Raise Err.Number Resume CleanExit End Sub 

Mulighet : Fordi det egendefinerte objektet vil være utenfor omfanget etter at feilen er opphevet, vil dens avslutningsmetode kjøres automatisk, noe som fører til at den anskaffede ressursen blir lukket / ryddet opp ordentlig.

En nødvendighet mindre for en «endelig» blokk.

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Feilhåndtering i Avslutt-metode

Etter min mening er det kontekstavhengig hvordan en feil blir håndtert i Avslutt-metoden i den tilpassede klassen. Kanskje det burde logges et sted i tillegg eller til og med svelges i det hele tatt?

Dette er sikkert diskutabelt.

Men det er viktig for aktiver en feilbehandler i denne metoden, fordi, så vidt jeg vet, vil en ubehandlet feil i denne metoden føre til at VBA bryter utførelsen og viser sin standard kjøretidsfeilmeldingsboks.

For å avklare mitt forrige innlegg, følgende linje fra HarveyFrenchs kode:

RememberErrLine = Erl() 

fungerer ikke med mindre linjenumre er lagt til i hver kodelinje. I stedet for å skrive linjenumre manuelt, noe som er altfor kjedelig, kan du bruke et verktøy for automatisk å legge til linjenumrene. Der er noen få verktøy der ute som kan gjøre dette, jeg bruker et som heter CodeLiner.

Her er koden med linjenumre, som gjør at Erl() kan fungere vellykket :

Option Compare Database Option Explicit Dim RememberErrNumber As Long Dim RememberErrDescription As String Dim RememberErrSource As String Dim RememberErrLine As Integer Private Sub RememberThenClearTheErrorObject() 10 11 On Error Resume Next 12 " For demo purposes 14 Debug.Print "ERROR RAISED" 15 Debug.Print Err.Number 16 Debug.Print Err.Description 17 Debug.Print Err.Source 18 Debug.Print " " 19 20 " This function has to be declared in the same scope as the variables it refers to 22 RememberErrNumber = Err.Number 23 RememberErrDescription = Err.Description 24 RememberErrSource = Err.Source 25 RememberErrLine = Erl() 26 " Note that the next line will reset the error object to 0, the variables above are used to remember the values " so that the same error can be re-raised 29 Err.Clear 30 " Err.Clear is used to clear the raised exception and set the err object to nothing (ie err.number to 0) " If Err.Clear has not be used, then the next "On Error GoTo ALabel" that is used in this or the procedure that called it " will actually NOT pass execution to the ALabel: label BUT the error is paseed to the procedure that called this procedure. " Using Err.Clear (or "On Error GoTo -1 ") gets around this and facilitates the whole TRY CATCH block scenario I am using there. 35 36 " For demo purposes 38 Debug.Print "ERROR RAISED is now 0 " 39 Debug.Print Err.Number 40 Debug.Print Err.Description 41 Debug.Print Err.Source 42 Debug.Print " " 43 " For demo purposes 45 Debug.Print "REMEMBERED AS" 46 Debug.Print RememberErrNumber 47 Debug.Print RememberErrDescription 48 Debug.Print RememberErrSource 49 Debug.Print " " 50 End Sub Private Sub ClearRememberedErrorObjectValues() 54 " This function has to be declared in the same scope as the variables it refers to 56 RememberErrNumber = 0 57 RememberErrDescription = "" 58 RememberErrSource = "" 59 RememberErrLine = 0 60 End Sub Sub ExampleOfTryCatchBlockInVBA() 67 68 On Error GoTo HandleError 69 70 " ----------------------------------------------------- " SubProcedure1 has the example of a multiple line TRY block with a block of code executed in the event of an error 73 74 SubProcedure1 75 76 77 78 Exit Sub 79 HandleError: 80 81 Select Case Err.Number 82 Case 0 " This shold never happen as this code is an error handler! " However if it does still allow the Err.raise to execute below. (In this case Err.raise will fail " and itself will raise an error "Invalid procedure call or argument" indicating that 0 cannot be used to raise and error! 86 87 Case 111111 " You might want to do special error handling for some predicted error numbers " perhaps resulting in a exit sub with no error or " perhaps using the Err.raise below 91 92 Case Else " Just the Err.raise below is used for all other errors 94 95 End Select 96 " " I include the procedure ManageErrSource as an exmple of how Err.Source can be used to maintain a call stack of procedure names " and store the name of the procedure that FIRST raised the error. " 101 Err.Raise Err.Number _ , ManageErrSource("MyModuleName", Err.Source, Erl(), "tsub1_RaisesProcedureNotFoundError") _ , Err.Number & "-" & Err.Description 104 " Note the next line never gets excuted, but I like to have resume in the code for when I am debugging. " (When a break is active, by moving the next executable line onto it, and using step over, it moves the exection point to the line that actually raised the error) 107 Resume 108 End Sub Sub SubProcedure1() 112 " ----------------------------------------------------- " Example of a multiple line TRY block with a Case statement used to CATCH the error 115 " " It is sometimes better to NOT use this technique but to put the code in it"s own procedure " (ie I refer to the code below that is surrounded by the tag #OWNSUB) . " However,sometimes using this technique makes code more readable or simpler! " 121 122 Dim i As Integer 123 " This line puts in place the defualt error handler found at the very foot of the procedure 125 On Error GoTo HandleError 126 127 " " Perhaps lots of statements and code here " 131 132 " First an example with comments 134 135 " ----------------------------------------------------- " TRY BLOCK START 138 " This next line causes execution to "jump" to the "catch" block in the event an error is detected. 140 On Error GoTo CatchBlock1_Start 141 " #OWNSUB 143 144 tsub_WillNotRaiseError_JustPrintsOk 145 146 If vbYes = MsgBox("1. Do you want to raise an error in the try block? - (PRESS CTRL+BREAK now then choose YES, try no later.)", vbYesNo) Then 147 i = 100 / 0 148 End If 149 " " Perhaps lots of statements and code here " 153 " #OWNSUB 155 " TRY BLOCK END " ----------------------------------------------------- 158 159 " ----------------------------------------------------- " CATCH BLOCK START 162 CatchBlock1_Start: 163 164 If Err.Number = 0 Then 165 On Error GoTo HandleError " Re-instates the procedure"s generic error handler " This is also done later, but I think putting it here reduces the likelyhood of a coder accidentally removing it. 168 169 Else 170 " WARNING: BE VERY CAREFUL with any code that is written here as " the "On Error GoTo CatchBlock1_Start" is still in effect and therefore any errors that get raised could goto this label " and cause and infinite loop. " NOTE that a replacement "On Error Goto" cannot be executed until Err.clear is used, otherwise the "On Error Goto" " will itself raise and error. " THEREFORE KEEP THE CODE HERE VERY SIMPLE! " RememberThenClearTheErrorObject should be the only code executed and this called procedure must be tight! 178 " This saves the details of the error in variables so that the "On Error GoTo HandleError" can be used " to determine how the next Err.Raise used below is handled (and also how any unexpected implicitly raised errors are handled) 181 RememberThenClearTheErrorObject 182 183 On Error GoTo HandleError "#THISLINE# 184 185 If vbYes = MsgBox("2. Do you want to raise an error in the erro handler? - (PRESS CTRL+BREAK now then try both YES and NO )", vbYesNo) Then 186 i = 100 / 0 187 End If 188 189 Select Case RememberErrNumber 190 Case 0: " No Error, do Nothing 191 192 Case 2517 193 Debug.Print "The coder has decided to just give a Warning: Procedure not found " & Err.Number & " - " & Err.Description 194 ClearRememberedErrorObjectValues " Not essential, but might save confusion if coding errors are made 195 196 Case Else " An unexepected error or perhaps an (user) error that needs re-raising occurred and should to be re-raised 198 " NOTE this is giving an example of what woudl happen if the CatchBlock1_ErrorElse is not used below 200 If vbYes = MsgBox("3. Do you want to raise an error in the ELSE error handler? CatchBlock1_ErrorElse *HAS NOT* been used? - (PRESS CTRL+BREAK now then try both YES and NO )", vbYesNo) Then 201 i = 100 / 0 202 End If 203 204 On Error GoTo CatchBlock1_ErrorElse 205 206 " SOME COMPLEX ERROR HANDLING CODE - typically error logging, email, text file, messages etc.. " Because the error objects values have been stored in variables, you can use " code here that might itself raise an error and CHANGE the values of the error object. " You might want to surround the code with the commented out CatchBlock1_ErrorElse lines " to ignore these errors and raise the remembered error. (or if calling a error handling module " just use on error resume next). " Without the CatchBlock1_ErrorElse lines any error raised in this "complex code" will be handled by the " active error handler which was set by the "On Error GoTo HandleError" tagged as "#THISLINE#" above. 215 216 If vbYes = MsgBox("4. Do you want to raise an error in the ELSE error handler when CatchBlock1_ErrorElse HAS been used? - (PRESS CTRL+BREAK now then try both YES and NO )", vbYesNo) Then 217 i = 100 / 0 218 End If 219 220 CatchBlock1_ErrorElse: 221 On Error GoTo HandleError " This line must be preceeded by an new "On error goto" for obvious reasons 223 Err.Raise RememberErrNumber, RememberErrSource, RememberErrDescription 224 225 End Select 226 227 On Error GoTo HandleError 228 229 End If " CATCH BLOCK END " ----------------------------------------------------- 232 On Error GoTo HandleError " Unnecessary but used to delimt the catch block 233 234 235 236 " " lots of code here perhaps " 240 241 242 243 " ----------------------------------------------------- " Example 2 " " In this example goto statements are used instead of the IF statement used in example 1 " and no explanitory comments are given (so you can see how simple it can look) " 250 " ----------------------------------------------------- " TRY BLOCK START 253 254 On Error GoTo CatchBlock2_Start 255 256 tsub_WillNotRaiseError_JustPrintsOk 257 258 If vbYes = MsgBox("Do you want to raise an error? - (PRESS CTRL+BREAK now then choose YES)", vbYesNo) Then 259 i = 100 / 0 260 End If 261 " " Perhaps lots of statements and code here " 265 " TRY BLOCK END " ----------------------------------------------------- 268 269 270 GoTo CatchBlock2_End: 271 CatchBlock2_Start: 272 273 RememberThenClearTheErrorObject 274 275 On Error GoTo HandleError 276 277 Select Case RememberErrNumber 278 Case 0: " No Error, do Nothing 279 280 Case 2517 281 Debug.Print "The coder has decided to just give a Warning: Procedure not found " & Err.Number & " - " & Err.Description 282 ClearRememberedErrorObjectValues " Not essential, but might save confusion if coding errors are made 283 284 Case Else " An unexepected error or perhaps an (user) error that needs re-raising occurred and should to be re-raised " In this case the unexpecetd erro will be handled by teh code that called this procedure " This line must be preceeded by an new "On error goto" for obvious reasons 288 Err.Raise RememberErrNumber, RememberErrSource, RememberErrDescription 289 290 End Select 291 292 On Error GoTo HandleError 293 294 End If 295 296 CatchBlock2_End: " CATCH BLOCK END " ----------------------------------------------------- 299 On Error GoTo HandleError " Unnecessary but used to delimt the catch block 300 301 302 303 " " Here you could add lots of lines of vba statements that use the generic error handling that is after the HandleError: label " " 308 " " You could of course, alway add more TRY CATCH blocks like the above " " 313 314 315 316 Exit Sub 317 HandleError: 318 319 Select Case Err.Number 320 Case 0 " This shold never happen as this code isan error handler! " However if it does still allow the Err.raise to execute below. (In this case Err.raise will fail " and itself will raise an error "Invalid procedure call or argument" indicating that 0 cannot be used to raise and error! 324 325 Case 111111 " You might watch to do special error handling for some predicted error numbers " perhaps exit sub " Perhaps using the Err.raise below 329 End Select 330 " ie Otherwise " " Note that I use the Err.Source to maintain a call stack of procedure names " 335 Err.Raise Err.Number _ , ManageErrSource("MyModuleName", Err.Source, Erl(), "tsub1_RaisesProcedureNotFoundError") _ , Err.Number & "-" & Err.Description 338 " Note the next line never gets excuted, but I like to have resume in the code for when I am debugging. " (By moving the next executable line onto it, and using step over, it moves the exection point to the line that actually raised the error) 341 Resume 342 End Sub Sub tsub_WillNotRaiseError_JustPrintsOk() 348 349 Static i As Integer 350 351 i = i + 1 352 353 Debug.Print "OK " & i 354 End Sub Public Function ManageErrSource(MyClassName As String, ErrSource As String, ErrLine As Integer, ProcedureName As String) As String 360 " This function would normally be in a global error handling module 362 " On Error GoTo err_ManageErrSource 364 365 Const cnstblnRecordCallStack As Boolean = True 366 367 Select Case ErrSource 368 369 Case Application.VBE.ActiveVBProject.Name 370 " Err.Source is set to this value when a VB statement raises and error. eg In Access by defualt it is set to "Database" 372 373 ManageErrSource = Application.VBE.ActiveVBProject.Name & " " & MyClassName & "." & ProcedureName & ":" & ErrLine 374 375 Case "" 376 " When writing code ouside of the error handling code, the coder can raise an error explicitly, often using a user error number. " ie by using err.raise MyUserErrorNumber, "", "My Error descirption". " The error raised by the coder will be handled by an error handler (typically at the foot of a procedure where it was raised), and " it is this handler that calls the ManageErrSource function changing the Err.Source from "" to a meaningful value. 381 382 ManageErrSource = Application.VBE.ActiveVBProject.Name & " " & MyClassName & "." & ProcedureName & ":" & ErrLine 383 384 Case Else 385 " This code is executed when ManageErrSource has already been called. The Err.Source will already have been set to hold the " Details of where the error occurred. " This option can be used to show the call stack, ie the names of the procdures that resulted in the prcedure with the error being called. 389 390 If cnstblnRecordCallStack Then 391 392 If InStr(1, ErrSource, ";") = 0 Then 393 ManageErrSource = ErrSource & ":: Called By: " 394 End If 395 ManageErrSource = ErrSource & ";" & ProcedureName & ":" & ErrLine 396 397 Else 398 ManageErrSource = ErrSource 399 400 End If 401 402 End Select 403 404 Exit Function 405 err_ManageErrSource: 406 Err.Raise Err.Number, "MyModuleName.err_ManageErrSource", Err.Description 407 Resume 408 End Function 

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