On 2010-03-09, at 2:01 PM, David Duncan wrote: > On Mar 8, 2010, at 7:44 PM, Philippe Sismondi wrote: > >> Here is my AppController's init method, in which instanceObj is set to an >> autoreleased MadeObj: >> > >> In other words, the MadeObj instance for AppController's instance variable >> is created and then immediately dealloc'd. I take this to mean that the >> autorelease pool it was in was released/drained. If I change the >> AppController init method to retain instanceMadeObj, the dealloc does not >> happen. > > When you use +alloc/-init on an object however, you are returned an object > that you own, thus it will not be deallocated until after you call -release > on that object (how soon after will depend on what other objects also own the > object). > > While your question was sparked by the behavior of an auto release pool, it > is really all about object ownership. Because in your example above you don't > own the object that you are referencing, it may be deallocated at any time, > leaving you with a dangling reference. When you switch to +alloc/-init you > instead get an object that you do own, which won't be deallocated until you > do release it. > > If this is still confusing, I would recommend that you continue taking a look > at the Memory Management guide until you've internalized this. It also > generally helps to not think about autorelease pools as anything more than an > implementation detail until you have gotten all of this down, as they won't > make a whole lot of sense to you until you understand how object ownership > works. > -- > David Duncan > Apple DTS Animation and Printing >
Thanks, David. I think I get it now. I *mostly* understood before posting, but my mistake - as I see it now - was to make unwarranted assumptions about the autorelease pool state outside the scope of my method. It seems that except for "inner" autorelease pools that I control explicitly, no assumptions can be made about what happens when. However, unless I am still mistaken, by "deallocated at any time" you mean outside the scope of my init method. That is, I suppose I could have used the autoreleased object within the scope of my init method without it being deallocated out from under me. But since I expect an instance variable to be valid after init returns, I had better retain it. Is that right? Thanks again. - Phil - _______________________________________________ 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: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
