[Pythonmac-SIG] PyObjC: debugging error-less crashes?

[Gary Bernhardt]

You need to wrap you alertEnded... method with
PyObjcTools.Apphelper.endSheetMethod:

@PyObjcTools.Apphelper.endSheetMethod
def alertEnded(self, alert, choice, context):
    ...

(Methods wrapped with endSheetMethod don't need the ObjC name
mangling, so you can name it whatever you want.)

I have a very weak understanding of why this is needed, but it's
something related to sheet callback methods not having a fixed
signature.

On Wed, Jul 23, 2008 at 11:57 AM, Daniel Ashbrook <anjiro at cc.gatech.edu> wrote:
> I'm working my way through the excellent book "Cocoa Programming for Mac OS
> X", but using PyObjC instead of ObjC. For the most part it's working very
> well - a testament to the awesomeness of PyObjC!
>
> However, I'm occasionally getting a crash from my application that gives no
> errors - it just enters into the debugger with no other output. A backtrace
> leads through C code to (inevitably) objc_msgSend(), which doesn't help
> much.
>
> In one case I managed to figure out that I needed to add myFunc_ =
> objc.accessor(myFunc_) after the definition of myFunc_() (though I have no
> clue why), but in the current case that doesn't help. The relevant chunk of
> code is below. My debug log shows the "Ending alert sheet" message, but not
> the "Alert ended" message.
>
>
> @IBAction
> def removeEmployee_(self, sender):
>    selectedPeople = self._employeeController.selectedObjects()
>    alert =
> NSAlert.alertWithMessageText_defaultButton_alternateButton_otherButton_informativeTextWithFormat_(u'Delete?',
> u'Delete', u'Cancel', None, u'Do you really want to delete %d people?' %
> len(selectedPeople))
>    NSLog(u'Starting alert sheet')
> alert.beginSheetModalForWindow_modalDelegate_didEndSelector_contextInfo_(self._tableView.window(),
> self, 'alertEnded:code:context:', None)
>    NSLog(u'Ending alert sheet')
>
>
> def alertEnded_code_context_(self, alert, choice, context):
>    NSLog(u'Alert ended')
>    if choice == NSAlertDefaultReturn:
>        self._employeeController.remove(None)
>
>
> Thanks in advance for any hints, whether general or specific!
>
>
>
> Daniel Ashbrook
> _______________________________________________
> Pythonmac-SIG maillist  -  Pythonmac-SIG at python.org
> http://mail.python.org/mailman/listinfo/pythonmac-sig
>



-- 
Gary
http://blog.extracheese.org