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Re: Garbage collection leak in simple Core Data application
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Re: Garbage collection leak in simple Core Data application


  • Subject: Re: Garbage collection leak in simple Core Data application
  • From: Rob Keniger <email@hidden>
  • Date: Fri, 28 Nov 2008 08:42:07 +1000


On 28/11/2008, at 7:13 AM, Mathieu Coursolle wrote:

Hi Cocoa developers,

I created a simple garbage collected Core Data application using the Xcode template.
I did not change much except that I added an empty window controller for my window,
which is the file's owner of my .xib.


I added logs in the init and finalize methods to make sure that each object created was
eventually finalized. However, I realized that even if the document is always finalized when
I close the window, its window controller is not. Let's say I open a new document and close
it right away and repeat the operation a few dozen times, I end up with all documents collected,
but a few window controller still to be collected. Even if I force the collector, they are not collected.


Even stranger, if I delete my only entity from my .xcdatamodel (which does nothing), then
everything gets collected as it should. How can a entity prevent an object from being collected?


You are adding the NSWindowController to your document using - addWindowController:, which retains the window controller. You must then release the window controller using -removeWindowController: so that the collector frees the object.

Do this in MyDocument.h:

#import <Cocoa/Cocoa.h>
@class MyWindowController;
@interface MyDocument : NSPersistentDocument {
	MyWindowController* newWindowController;
}
@end

and change these methods in MyDocument.m:

- (void)makeWindowControllers
{
	// Create the project window controller and keep a reference to it.
	newWindowController = [[MyWindowController alloc] init];
	[newWindowController setShouldCloseDocument:YES];

	// Add it to the list of window controllers for this document.
	[self addWindowController:newWindowController];
}

- (void)finalize
{
	[self removeWindowController:newWindowController];
	NSLog(@"Document finalized");
	UpdateDocumentCount(0);
	[super finalize];
}


-- Rob Keniger



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 >Garbage collection leak in simple Core Data application (From: Mathieu Coursolle <email@hidden>)

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