Mailing Lists: Apple Mailing Lists
Image of Mac OS face in stamp
What to use observeValueForKeyPath: context
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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?

Thanks,

-Dave

_______________________________________________

Cocoa-dev mailing list (email@hidden)

Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com

Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden




Visit the Apple Store online or at retail locations.
1-800-MY-APPLE

Contact Apple | Terms of Use | Privacy Policy

Copyright © 2011 Apple Inc. All rights reserved.