To End Or Not To End. But How To End
in [Visual Basic]
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From: AR88 Enthusiast on 3 Apr 2010 07:25 I'm only raw beginner but what about unload me? <ducks while experts throw things> "Bee" <Bee(a)discussions.microsoft.com> wrote in message news:97B227F0-BB50-4D26-B16C-56C12F432F35(a)microsoft.com... > Down in the bowels of my VB6 app I need to ask the user to do something or > "die". > That is the way it is and I cannot change this structure. > I have seen applications that use >>> End <<<. > And I have seen many comments about NOT using End. > So > (1) what exactly does End do that is so bad? > (2) seen Stop too. > (3) how can I exit the app politely but immediately? > > How about calling a sub in a module that calls _unload in the main form? > > However, there may be flags set that the main form is supposed to process > so > I would have to clear all of those and not do that processing. > > Educate me. >
From: Mayayana on 3 Apr 2010 11:07 I always use a Sub Main and an ending sub I call DropIt, for anything more than 1 form. It seems to work best to do things from QueryUnload. You can call your version of DropIt from anywhere in code, but you may need to handle other closing messages, too, like a click on the X in the control box. See the QueryUnload docs for options. UnloadMode tells you where the quit message is coming from. For instance, if the person clicks the form close X in the control box, but they're in the middle of an operation, you might want to show a msgbox: If UnloadMode = 0 and SomethingElse = True then cancel = 1 ' stop the shutdown. Ret = Msgbox("Are you sure you want to quit?", 36) If Ret = 6 then Dropit ElseIf UnloadMode = 1 then 'called from code. '--confirm quit here Else DropIt '-- UnloadMode is > 1. No choice here, Just quit. End If
From: Mayayana on 3 Apr 2010 11:16 One other point I should have mentioned: Assuming you have multiple forms with control boxes, and only one is the main program form, you'll want to block those from unloading or calling your shutdown sub unexpectedly: If unloadmode = 0 then cancel = 1 FormThis.Hide End If
From: Nobody on 3 Apr 2010 13:12 "Bee" <Bee(a)discussions.microsoft.com> wrote in message news:97B227F0-BB50-4D26-B16C-56C12F432F35(a)microsoft.com... > Down in the bowels of my VB6 app I need to ask the user to do something or > "die". > That is the way it is and I cannot change this structure. > I have seen applications that use >>> End <<<. > And I have seen many comments about NOT using End. > So > (1) what exactly does End do that is so bad? > (2) seen Stop too. > (3) how can I exit the app politely but immediately? > > How about calling a sub in a module that calls _unload in the main form? > > However, there may be flags set that the main form is supposed to process > so > I would have to clear all of those and not do that processing. What specific situation are you after? If you have a Timer that you are using in frmMain to process stuff, you can add a public routine to frmMain, "CloseMe" that disables the Timer and clear any flags before unloading other forms.
From: Helmut Meukel on 3 Apr 2010 15:16
"Bee" <Bee(a)discussions.microsoft.com> schrieb im Newsbeitrag news:97B227F0-BB50-4D26-B16C-56C12F432F35(a)microsoft.com... > Down in the bowels of my VB6 app I need to ask the user to do something or > "die". > That is the way it is and I cannot change this structure. > I have seen applications that use >>> End <<<. > And I have seen many comments about NOT using End. > So > (1) what exactly does End do that is so bad? > (2) seen Stop too. > (3) how can I exit the app politely but immediately? > > How about calling a sub in a module that calls _unload in the main form? > > However, there may be flags set that the main form is supposed to process so > I would have to clear all of those and not do that processing. > > Educate me. > Hmmm, I've heard many arguments over the years against End and I know most are valid. Just let me tell you all a real life story: Some 10 years ago, I was working on a customers site to upgrade one of my own programs, when they had a problem with one of their knitting machines. Some of those machines were enhanced with NT4-boxes with some i/o-cards connected to the machine. I had also worked as subcontractor for the engeneering company who built those systems and programmed the data access part of their program. They used this NT4-box instead of a PLC to control the knitting machine to produce made-to-measure stockings. On one of the boxes the program refused to start, saying "Can't run twice". I checked it with taskmanager and there really was already an instance of the program without showing up on the screen. I asked some questions and found it only happend on one box, and their last resort was to power down machine and NT4-box and restart both. I telephoned with the engeneering company and they said they knew but had nobody who could come in the next 6 or 8 weeks. "Hey, can't you look into it?" I did and found the program tried to shut down after some communication problem with the machine and failed. When started again it looked if there was already an instance running, found the old no longer responding instance and stopped execution. This was intended, you can't have two instances of the program concurrently controlling the machine. I had never looked into the code controlling the machine and found at first glance nothing that could cause this shut-down failure. Debugging wasn't easy, even just running the program within the IDE on the NT4-box could create new errors due to the overhead of the IDE on a box with only 16 MB memory. So I inserted an End statement, compiled the app and let it run. I was for some more days there and my "fix" seemed to work without obvious problems. I wrote a report to the engeneering company, and warned that it was a quick-and-dirty solution and they should try to find the real cause and fix it. Some years later I was hired by the engeneering company to combine the different versions of this program into one. They had different versions due to hardware differences, i/o-cards sitting in different slots with different addresses... and when they fixed some bug in one version they hadn't always checked the other versions if the fix was needed there too. During this work I found they had ignored my warning, instead they had added the End statement to the other versions, too. I called one of the bosses and tried to convince him to let me search the cause of the glitch and really fix it. I got the answer: "We couldn't find the source of the glitch and the End worked just fine, so let it there, we don't intend to spend more money on this!" Two years ago the knitting company went out of business, the machines and the NT4-boxes were sold to Italy. I never heard anything about it, the program with the End statement will probably still run there. Helmut. |