I had a similar one the other week, same idea, notification I wanted to remove
in its handler.
I assume that before you added __block you were getting an exception in the
block handler, EACCESS was mine I think.
I also changed to a block variable and it started working. My presumption was
that observer was being captured as nil, or some unassigned value into the
block as the method was entered and thus was rubbish when the callback came and
as it was not a block variable the later assignment did not change the value
captured in the block. I also assumed that making it a block variable allowed
the captured observer to be changed to the result of addObserver:.. at the end
of the method call and be available to the block.
And yes I now love blocks too, especially with all the asynchronous methods
icloud uses. It's great in an open callback for a document to throw a block on
the main queue to close it again on the next cycle, and do something else when
the close callback comes.
On 16 Feb, 2012, at 4:58, Matt Neuburg <m...@tidbits.com> wrote:
> This appears to be working from all points of view (thank you, Instruments!):
>
> MyMandelbrotOperation* op =
> [[MyMandelbrotOperation alloc] initWithSize:self.bounds.size
> center:center zoom:1];
> __block __weak id observer = [[NSNotificationCenter defaultCenter]
> addObserverForName:@"MyMandelbrotOperationFinished"
> object:op queue:[NSOperationQueue mainQueue]
> usingBlock:^(NSNotification *note) {
> MyMandelbrotOperation* op2 = note.object;
> CGContextRef context = [op2 bitmapContext];
> if (self->bitmapContext)
> CGContextRelease(self->bitmapContext);
> self->bitmapContext = (CGContextRef) context;
> CGContextRetain(self->bitmapContext);
> [self setNeedsDisplay];
> [[NSNotificationCenter defaultCenter] removeObserver:observer
> name:@"MyMandelbrotOperationFinished" object:op2];
> }];
> [self.queue addOperation:op];
>
> This is delightful. I'm not leaking self, my operations are being dealloced
> in good order, I'm successfully registering and deregistering, I'm
> trampolining to the main thread without writing a trampoline method, I'm
> avoiding the nightmare of storing my observers in an instance variable, op
> and op2 are the same object - everything about it seems to be okay. My
> questions are:
>
> * Is this really an okay way to talk?
>
> * Why was I crashing until I said __block?
>
> m.
>
> --
> matt neuburg, phd = m...@tidbits.com, http://www.apeth.net/matt/
> pantes anthropoi tou eidenai oregontai phusei
> Programming iOS 5! http://shop.oreilly.com/product/0636920023562.do
> RubyFrontier! http://www.apeth.com/RubyFrontierDocs/default.html
> TidBITS, Mac news and reviews since 1990, http://www.tidbits.com
>
>
>
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