Re: NSArrayController and threading
Re: NSArrayController and threading
- Subject: Re: NSArrayController and threading
- From: Joe Chan <email@hidden>
- Date: Wed, 22 Dec 2004 16:27:25 -0500
After some experiments I found the following interesting facts:
- In order for changes to occur, -willChangeValueForKey: is definitely
needed.
- For some reason -didChange:valuesAtindexes:forKey: doesn't work, but
-didChangeValueForKey: does.
My model objects roughly look like this:
@interface Record : NSObject
{
NSMutableDictionary *_data;
}
...
- (void)loadThumbnail; // called within the thread to load the image
- (NSImage*)thumbnail; // return some default image if not loaded yet
@end
@interface Document : NSDocument
{
NSMutableArray *_recordList;
}
- (NSMutableArray*)recordList;
- (void)startLoadFiles;
- (void)loadFiles;
- (void)fileLoaded: (NSIndexSet *) indexes;
@endif
Inside fileLoaded:, I have to do something like this:
- (void)fileLoaded: (NSIndexSet *) indexes
{
Record *rec = [_recordList objectAtIndex: [indexes firstIndex]];
[rec willChangeValueForKey: @"thumbnail"];
[rec didChangeValueForKey: @"thumbnail"];
/* This doesn't work
[self willChange: NSKeyValueChangeReplacement valuesAtIndexes:indexes
forKey:@"thumbnail"];
[self didChange: NSKeyValueChangeReplacement valuesAtIndexes:indexes
forKey:@"thumbnail"];
*/
}
Which seems very strange to me. Is this a bug in the binding stuff, or
am I not understanding willChange:valuesAtIndexes:forKey: right?
On Dec 22, 2004, at 4:08 PM, John C. Randolph wrote:
On Dec 22, 2004, at 6:29 AM, Joe Chan wrote:
This approach is much simpler than my initial guess. The loading of
thumbnail works, however, the table is not getting updated with the
thumbnails until I scroll. Unfortunately, because binding eliminated
almost all the glue code, it also makes it very hard to debug why
it's not getting updated. I thought that once the didChange: is
called, the NSArrayController will trigger an update on the
NSImageCell and should redraw itself.
Hmm.. I wrote the code off the top of my head, and haven't tested it
in an app. You might try sending -willChangeValueForKey: before
-didChange:valuesAtIndexes:forKey:.
-jcr
John C. Randolph <email@hidden> (408) 974-8819
Sr. Cocoa Software Engineer,
Apple Worldwide Developer Relations
http://developer.apple.com/cocoa/index.html
--
Joe Chan
Sun Microsystems, Inc.
Burlington, MA
Tel: (781) 442-0809
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