I've run into some frustrating and confusing problems related to
memory management. I have an NSDocument subclass (MyDocument) with
several instance variables. One of those instance variables is an
NSDictionary called possibleColumns. The setter for possibleColumns
is dead simple:
If I set that instance variable at all, I run into a big problem.
The first document created by my app upon opening works fine.
However, if I open another document, it's instance variables seem to
be completely messed up. Specifically, one of the instance
variables, myWindow, is an IBOutlet set in the nib file to point to
the window for the document. Somehow, the instance docWindow ends up
pointing to (seemingly) random other objects in the second (and
third, etc) document created in my app. This creates serious
problems including hard crashes for obvious reasons when the program
tries to do things to/with to docWindow. This odd behavior goes away
if I never set possibleColumns. Any idea why this might be?
Further confusing matters, MyDocument's dealloc method doesn't get
called when a document window is closed. However, if I remove the
retain message in the setPossibleColumns: method, then MyDocument's
dealloc method does get called. Of course, I need to retain
possibleDocuments otherwise it ends up getting released out from
under MyDocument when I need it. Why should the presence or absence
of [possibleColumns retain]; in that setter method (and that's the
only line I'm changing in the whole project) change whether or not
dealloc gets called on MyDocument? Removing the retain message also
causes the problems with instance variables in later documents being
corrupt to disappear, but again, if I don't retain possibleColumns I
get crashes related to accessing a released object.
I'm really at a loss for further things to try here. Any thoughts?
Thanks,
Andrew
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