What to use observeValueForKeyPath: context
What to use observeValueForKeyPath: context
- Subject: What to use observeValueForKeyPath: context
- From: Dave Dribin <email@hidden>
- Date: Fri, 29 Aug 2008 09:56:11 -0500
Hi all,
It seems that KVO best practice is to use the "context" in
observeValueForKeyPath:ofObject:change:context: to differentiate
between different key paths, rather than check key path strings for
equality. Since context is a void *, it also seems best practice to
just use some unique pointer values. For example, mmalc's Graphics
Bindings sample does this:
static void *PropertyObservationContext = (void *)1091;
static void *GraphicsObservationContext = (void *)1092;
static void *SelectionIndexesObservationContext = (void *)1093;
I'm not quite understanding the point of using number values like
this, though. Won't using unique string literals (char * or NSString
*) also work?
static NSString *PropertyObservationContext = @"Property Context";
static NSString *GraphicsObservationContext = @"Graphics Context";
static NSString *SelectionIndexesObservationContext = @"Selection
Indexes Context";
Is there some benefit to using number values over string constants, or
is it just stylistic differences?
Thanks,
-Dave
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