On 30/07/2013, at 7:43 PM, Quincey Morris <quinceymor...@rivergatesoftware.com> wrote:
> On Jul 30, 2013, at 10:26 , Graham Cox <graham....@bigpond.com> wrote: > >> How often have you encountered an unexpected exception from some low-level >> code you don't own under circumstances you can't control? If your app >> crashed every time you'd soon have a reputation for unreliability that is in >> all probability undeserved. On balance it's better to carry on with some >> minor glitch than "quit unexpectedly". > > Surely the problem with this perspective is that the uncaught exception > results in an abrupt transfer of control from the point of the exception back > to (approximately) [NSApplication sendEvent:]? > > If you don't own the low-level code where the exception was thrown, you can > have no confidence that non-stack data structures being maintained by that > code -- along with all of the intermediate levels of calling code -- are in > any usable state. > I totally agree - from the point of view of a developer. However, from the point of view of a) the user and b) the director of a company making and selling apps, it's not what you want to happen. Any crash is unacceptable - it makes the app look flaky and the user will lose faith in it and probably lose their data too. The vast majority of exceptions in practice are benign - much better to effectively ignore them and continue as best you can (which is very often with 100% functionality) than crash. If there are cases that come up that can be handled better, then those handlers can be added in later. As an example, I had one recently where under very specific circumstances, the user could end up pushing the code into inverting a transform that had no inverse, e.g. a divide by zero. The Core Graphics framework throws an exception if you do that, but the specific circumstances had not been caught in testing because it was such a weird corner case. If my app crashed at that point, it would look very serious indeed, whereas the actual outcome for the user was a very minor graphical glitch. I now add a handler for that case that puts things back in a good state, but simply ignoring the original exception wasn't a disaster either. --Graham _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
