Re: Async NSURLConnection + Concurrent NSOperation = Not possible under Mac OS X 10.6?
Re: Async NSURLConnection + Concurrent NSOperation = Not possible under Mac OS X 10.6?
- Subject: Re: Async NSURLConnection + Concurrent NSOperation = Not possible under Mac OS X 10.6?
- From: "Adam R. Maxwell" <email@hidden>
- Date: Sun, 30 Aug 2009 11:47:51 -0700
On Aug 30, 2009, at 10:18 AM, Ken Thomases wrote:
On Aug 30, 2009, at 10:29 AM, Steven Degutis wrote:
I either would need to use NSURLConnection in a stand-alone class,
or use it
synchronously inside a non-concurrent NSOperation subclass. (Please
correct
me if I'm wrong!)
As Adam Maxwell said, you can use a non-concurrent operation which
uses the asynchronous NSURLConnection APIs and runs the run loop
itself. Handling cancel may require that you send a message from
whatever thread invoked -cancel to the thread on which your
operation is running, which may be non-trivial.
What messaging between threads is required? My suggestion is to
periodically check [self isCancelled] and run the runloop with a
timeout, and bail out if that's true. You have to do this anyway in
order to support cancellation, since it doesn't stop anything on its
own.
Another approach to consider is to make a concurrent operation which
actually shunts its work to the main thread using -
performSelectorOnMainThread:... So, NSOperationQueue would invoke -
start on whichever thread it likes (you shouldn't rely on it being
or not being anything in particular). -start would perform a
selector on the main thread that creates the NSURLConnection and
starts the download. As a consequence, it will be tied to the main
thread's run loop. As data arrives, NSURLConnection will invoke
your delegate methods on the main thread, too, so they shouldn't
block or do long computations. (If you want to do long computations
with the result of the download, you should queue up a separate
operation for that once the download has completed.) Your operation
class will probably want to respond to -cancel by sending -cancel to
the NSURLConnection; this, too, must be shunted to the main thread.
That would probably work pretty well, assuming that generating
isExecuting/isFinished KVO notifications on the main thread is okay.
Attachment:
smime.p7s
Description: S/MIME cryptographic signature
_______________________________________________
Cocoa-dev mailing list (email@hidden)
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:
This email sent to email@hidden