Async NSURLConnection and blocks (was: Running NSURLConnection from within an NSOperation?)
Async NSURLConnection and blocks (was: Running NSURLConnection from within an NSOperation?)
- Subject: Async NSURLConnection and blocks (was: Running NSURLConnection from within an NSOperation?)
- From: John Heitmann <email@hidden>
- Date: Sun, 20 Jun 2010 13:42:55 -0700
On Feb 9, 2010, at 3:01 PM, Keith Duncan wrote:
> ...you should create a 'concurrent' NSOperation as described in the documentation, and schedule your NSURLConnection on +[NSRunLoop mainRunLoop]. This will allow your NSOperation -start method to exit immediately and the thread to return to the pool.
I had a working async NSURLConnection scheme where I initialized the connection in a new thread and pumped its run loop manually on that thread until I saw the delegate set a completion flag. I thought I'd convert it to blocks since it cleans up some ugly code there. I'm 95% of the way there and things look good, but there are some lingering problems in my code that I don't understand. The above tip helped with one of my problems: the automatic block thread didn't pump the NSURLConnection run loop, so I scheduled the connection in the main run loop like Keith suggested and things worked. My first question is: doesn't this block the main loop with io? I have another version which uses a block to manually pump, but then this ties up an automatic block thread, which are supposed to be short-lived. Is it really a good practice to drive the NSURLConnection from the main loop?
My second question is: How do I memory manage the autorelease pool that the delegate uses? Here's a rough idea of what I have now:
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{
__block NSAutoreleasePool *autoReleasePool = [[NSAutoreleasePool alloc] init];
NSURLConnection *connection = [NSURLConnection alloc];
ResponseHandler *handler = [ResponseHandler alloc];
[handler initWithDelegate:delegate
completionBlock:^{dispatch_async(queue, ^{
[connection release];
[handler release];
[autoReleasePool release];
[delegate release];
});}];
[connection initWithRequest:urlRequest delegate:handler startImmediately:NO];
[connection scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
[connection start];
});
ResponseHandler is pretty simple. It processes the data and calls the completionBlock when done. With that code I get "attempt to pop an unknown autorelease pool". When I drop the release altogether the error goes away, but that seems like a leak.
John_______________________________________________
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