Hello Cocoa-Meisters,
My Document-based OS X program is parsing huge ASCII data files in an
NSOperationQueue, and then displays the data in a graph.
It works, however I've seen 2 different approaches to update the User-Interface
(UI) after the NSOperation has finished (please check code below):
1. With KVO in a Controller object: Observing the NSOperation's "isFinished"
value and then in observeValueForKeyPath:ofObject:change:context:
update the UI (graph display) on the main thread with
performSelectorOnMainThread:withObject:waitUntilDone
2. No KVO: in NSOperation the UI is updated after the parsing is done, by
calling the delegate again with
performSelectorOnMainThread:withObject:waitUntilDone
I've tested both approaches but can't decide which one is the most correct /
best, or what are the benefits of using one approach or another ?
Any suggestions or help is greatly appreciated..
Regards,
Gilles
Some code snippets here:
//-----------------------------------------------
// 1. With KVO in a Controller object
//-----------------------------------------------
MyController.m
...
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
change:(NSDictionary *)change context:(void *)context
{
....
// Update the User-Interface and graph view
if ( [keyPath isEqual:@"isFinished"] && asciiParserOperation == object )
{ ...
[self
performSelectorOnMainThread:@selector(operationAsciiParsingDone:)
withObject:[asciiParserOperation parsedFile] waitUntilDone:NO];
}
....
}
//-----------------------------------------------
// 2. NSOperation with delegate
//-----------------------------------------------
-(void)main
{
@autoreleasepool {
// Do the parsing here
parsedAscii = [[AsciiParser alloc]
initWithContentsOfString:myAsciiString]
// Update the User-Interface and graph view via delegate
if( self.delegate && [self.delegate
respondsToSelector:@selector(operationAsciiParsingDone:)] )
{
[(NSObject*)delegate
performSelectorOnMainThread:@selector(operationAsciiParsingDone:)
withObject:[self parsedAscii]
waitUntilDone:NO];
}
}
.....
}
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