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Last active December 17, 2015 08:48
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This gist includes a quick syntax for constructing NSIndexSets—[@0:9] and [@0:9 step:2]—and fast enumeration support for NSIndexSet (yielding NSNumbers). The result is that you can enumerate over ranges using for/in. The gist is CodeRunner ready.
#import <Foundation/Foundation.h>
@interface NSNumber (range)
- (NSIndexSet*):(NSUInteger)max;
- (NSIndexSet*):(NSUInteger)max step:(NSUInteger)step;
@end
@interface NSIndexSet (FastEnumeration) <NSFastEnumeration> @end
int main(int argc, char *argv[]) {
@autoreleasepool {
NSLog(@"vars = %@", [@0:20 step:2]);
for(NSNumber * i in [@0:20 step:2]) {
NSLog(@"i = %ld", i.integerValue);
}
}
}
@implementation NSNumber (range)
- (NSIndexSet*):(NSUInteger)max {
return [self:max step:1];
}
- (NSIndexSet*):(NSUInteger)max step:(NSUInteger)step {
NSMutableIndexSet * indexes = [NSMutableIndexSet new];
for(NSUInteger i = self.unsignedIntegerValue; i <= max; i += step) {
[indexes addIndex:i];
}
return indexes;
}
@end
@implementation NSIndexSet (FastEnumeration)
- (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState *)state objects:(__unsafe_unretained id *)stackbuf count:(NSUInteger)len {
if(state->state == 0) {
// There's no good way to check for mutations without access to NSMutableIndexSet's internals, so we just set a pointer that we know will be valid and won't change.
state->mutationsPtr = state->extra;
}
NSUInteger index = [self indexGreaterThanOrEqualToIndex:state->state];
if(index == NSNotFound) {
return 0;
}
__autoreleasing NSNumber * temp = @(index);
state->state = index + 1;
state->itemsPtr = stackbuf;
state->itemsPtr[0] = temp;
return 1;
}
@end
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