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Re: How to make Obj-C collection subscripting work on iOS 5?
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Re: How to make Obj-C collection subscripting work on iOS 5?


  • Subject: Re: How to make Obj-C collection subscripting work on iOS 5?
  • From: Rainer Brockerhoff <email@hidden>
  • Date: Mon, 20 Aug 2012 20:41:47 -0300

On Aug 20, 2012, at 19:41 , email@hidden wrote:
> Date: Mon, 20 Aug 2012 15:16:43 -0700
> From: Greg Parker <email@hidden>
> Message-ID: <email@hidden>
>
> On Aug 20, 2012, at 2:02 PM, Jens Alfke <email@hidden> wrote:
>> On Aug 20, 2012, at 12:52 PM, I wrote:
>>> My first thought was to declare some categories on NSArray and NSDictionary to define those methods, but that's likely to cause issues when iOS 6 comes out and already includes those methods — I'll get compile errors (which I can work around with #ifdefs) but also a warning at launch time because the methods are declared in two places.
>
> IIRC there are some subscript-able classes that libarclite does not upgrade (NSOrderedSet, maybe?) so you still need to test thoroughly on older deployment targets.


I can confirm NSOrdered[Mutable]Set isn't covered by libarclite. Here's what I'm using for that (easily extended to other classes:

@interface NSOrderedSet()
- (id)objectAtIndexedSubscript:(NSUInteger)idx;
@end

@interface NSMutableOrderedSet()
- (void)setObject:(id)obj atIndexedSubscript:(NSUInteger)idx;
@end

static void PatchClass(Class class ,SEL newsel, SEL oldsel) {
	id instance = [[class alloc] init];
	class = [instance class];
	[instance release];
	if (![class instancesRespondToSelector:newsel]) {
		if ([class instancesRespondToSelector:oldsel]) {
			Method method = RBXCALL(class_getInstanceMethod)(class, oldsel);
			if (method) {
				IMP imp = RBXCALL(method_getImplementation)(method);
				if (imp) {
					const char* enc = RBXCALL(method_getTypeEncoding)(method);
					if (enc) {
						RBXCALL(class_addMethod)(class, newsel, imp, enc);
					}
				}
			}
		}
	}
}

static void SetObjectSwapped(id myself, SEL _cmd, id obj,NSInteger idx) {
	[myself replaceObjectAtIndex:idx withObject:obj];
}

static void PatchClassSwap(Class class, SEL newsel) {
	id instance = [[class alloc] init];
	class = [instance class];
	[instance release];
	if (![class instancesRespondToSelector:newsel]) {
		if ([class instancesRespondToSelector:@selector(replaceObjectAtIndex:withObject:)]) {
			RBXCALL(class_addMethod)(class, newsel, (IMP)SetObjectSwapped, "v@:@q");
		}
	}
}

...and early in the app's startup I call:

	PatchClass([NSOrderedSet class], @selector(objectAtIndexedSubscript:), @selector(objectAtIndex:));
	PatchClass([NSMutableOrderedSet class], @selector(objectAtIndexedSubscript:), @selector(objectAtIndex:));
	PatchClassSwap([NSMutableOrderedSet class], @selector(setObject:atIndexedSubscript:));

This runs fine on both 10.7 and 10.8, so it should also work on iOS5 and iOS6.

HTH,
--
Rainer Brockerhoff  <email@hidden>
Belo Horizonte, Brazil
"In the affairs of others even fools are wise
In their own business even sages err."
Weblog: http://www.brockerhoff.net/blog


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