Re: Binding and multithreading
Re: Binding and multithreading
- Subject: Re: Binding and multithreading
- From: Dave Fernandes <email@hidden>
- Date: Fri, 23 Mar 2012 19:14:52 -0400
See the Cocoa Design Patterns doc:
"The Receptionist Design Pattern in Practice
A KVO notification invokes the observeValueForKeyPath:ofObject:change:context: method implemented by an observer. If the change to the property occurs on a secondary thread, theobserveValueForKeyPath:ofObject:change:context: code executes on that same thread."
So you shouldn't use observeValueForKeyPath:ofObject:change:context to update the GUI in this context. I don't know of any better method than what the OP suggested.
Cheers,
Dave
On 2012-03-23, at 6:32 PM, Jan E. Schotsman wrote:
> Jonathan Taylor wrote:
>> I have been struggling with a problem which I think I have eventually realised is down to me not handling multithreading issues properly. The situation is I have some computationally-demanding code that is running in a separate thread. This has input parameters and state variables associated with it. For diagnostic reasons I would like to be able to display the values of the state variables in the GUI. I had intended to do this just by binding to them. However I am getting occasional "message sent to deallocated instance" errors which I suspect are a symptom of the fact that I am Doing It Wrong. Further reading suggests that because of the way bindings work, modifying those state variables is leading to binding/gui type stuff happening away from the main thread, which appears not to be permitted.
> I use KVO for this. Have your main thread observe the state variables (declared as properties) and update the GUI in your observeValueForKeyPath:ofObject:change:context: method.
> I hope this is elegant enough for you ;-)
> Jan E.
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