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What to use observeValueForKeyPath: context
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What to use observeValueForKeyPath: context

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?




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