Hi Adam You really need a reply from Rolf or Sebastian, but they are in Boston at the moment at the (annual?) company meetup. I've CCed them, but I dont know how much spare time they have this week.
So, just so this doesn't drop off the bottom of the list, this SO item from Miguel explains it well: http://stackoverflow.com/questions/5623223/no-constructor-found-for-viewcontroller-ctorsystem-intptr I suspect that it might be a case where you need to keep a reference to the object in a class-local variable, rather than a method-local one or just assigning it to a (obj-c?) object. I've never really implemented them, tho maybe I should :). I used to have the same exceptions as this, but I've not seen it in live debug logs for ages - it's possible that the GC got fixed (or improved) Drop the list an email back if that doesn't answer your question Cheers Nic On Fri, Jul 27, 2012 at 8:10 PM, Adam Kemp <[email protected]> wrote: > I'm hitting a crash when receiving memory warnings in some situations. In > one view controller (A) we are handling the memory warning by calling > Dispose() on another view controller (B) which is no longer necessary. > Unfortunately, something later on during the process of the (native) > memory warning handling code is trying to call a method in view controller > B, and it's trying to construct a managed object to do so. This causes an > exception because I don't have a constructor which takes an IntPtr so the > runtime can't construct the managed object. > > I know that if implementing the IntPtr constructor the crash doesn't > occur. I also know that it goes away if I remove the call to Dispose, but > I don't think that's a guaranteed fix since the object could still be > GCed. I'm looking for the "right" fix, but I have several unanswered > questions about what is going on that I need to find an answer to in order > to find it. > > The first question is what method is being called on view controller B, > and why is it wanting a managed object to call that method? I don't have > an override for DidReceiveMemoryWarning or ViewDidUnload. In fact, the > only override in that view controller (which inherits directly from > UITableViewController) is ViewDidLoad. The exception tells me "Selector > invoked from objective-c on a managed object (0xB9E72D0) that has been > GC'ed", but it won't tell me which selector was invoked. In a simpler test > case that I created I could only reproduce the crash if I overrode either > DidReceiveMemoryWarning or ViewDidUnload, but in my full application I get > the crash even though I haven't implemented either. I don't understand > why. Is there a trick to figuring out which method is being invoked when > this exception occurs? > > The second question is what are the rules for when we are expected to > implement the IntPtr constructor for classes that inherit from NSObject? I > don't want to blindly add it to every class, especially since in some > cases it probably can't be implemented in a sane way at all (the Dispose > method might have released resources that you can't get back without > arguments from a real constructor). Is there some rule for this? Does my > situation fit that rule? > > Thanks. > -- > Adam Kemp > [email protected] > (512) 683-6058 > _______________________________________________ > MonoTouch mailing list > [email protected] > http://lists.ximian.com/mailman/listinfo/monotouch -- Nic Wise t. +44 7788 592 806 | @fastchicken | http://www.linkedin.com/in/nicwise b. http://www.fastchicken.co.nz/ mobileAgent (for FreeAgent): get your accounts in your pocket. http://goo.gl/IuBU Trip Wallet: Keep track of your budget on the go: http://goo.gl/ePhKa Earnest: Self-employed? Track your business expenses and income. http://earnestapp.com Nearest Bus: find when the next bus is coming to your stop. http://goo.gl/Vcz1p London Bike App: Find the nearest Boris Bike, and get riding! http://goo.gl/Icp2 _______________________________________________ MonoTouch mailing list [email protected] http://lists.ximian.com/mailman/listinfo/monotouch
