Here’s a category for getting the index path to an object stored in nested NSArrays:

@interface NSArray (MBIndexPath)

• (id)objectAtIndexPath:(NSIndexPath *)indexPath; // Raises an NSRangeException if the indexPath goes beyond the bounds of the receiver.
• (NSIndexPath *)indexPathOfObject:(id)object; // Returns nil if the object does not exist within the receiver. @end

@interface NSArray (MBIndexPathPrivate)

• (NSUInteger *)createIndexesOfPathToObject:(id)object count:(NSUInteger *)count; // Returns a dynamically allocated array which must be freed by the caller. *count must be 0 when passed in. @end

@implementation NSArray (MBIndexPath)

• (id)objectAtIndexPath:(NSIndexPath *)indexPath; { if (indexPath == nil) [NSException raise:NSInvalidArgumentException format:nil];

  id object = self; NSUInteger i; for (i = 0; i < [indexPath length]; i++) { if ([object isKindOfClass:[NSArray class]] == NO || [object count] <= [indexPath indexAtPosition:i]) [NSException raise:NSRangeException format:nil]; object = [object objectAtIndex:[indexPath indexAtPosition:i]]; }

  return object; }

• (NSIndexPath *)indexPathOfObject:(id)object; { if (object == nil) [NSException raise:NSInvalidArgumentException format:nil];

  NSUInteger count = 0; NSUInteger *indexes = [self createIndexesOfPathToObject:object count:&count];

  if (indexes == NULL) return nil;

  NSIndexPath *indexPath = [NSIndexPath indexPathWithIndexes:indexes length:count]; free(indexes); return indexPath; }

// NSArray (MBIndexPathPrivate)

• (NSUInteger )createIndexesOfPathToObject:(id)object count:(NSUInteger *)count; { if (count == NSUIntegerMax) return NULL; (*count)++;

  NSUInteger i; for (i = 0; i < [self count]; i++) { if (self objectAtIndex:i] isEqual:object]) { [[NSUInteger indexes = malloc(count * sizeof(NSUInteger)); if (indexes == NULL) { count = NSUIntegerMax; return NULL; } indexes[count - 1] = i; return (indexes + count - 1); } else if (self objectAtIndex:i] isKindOfClass:[[[NSArray class]]) { NSUInteger *indexes = self objectAtIndex:i] createIndexesOfPathToObject:object count:count]; if (count == [[NSUIntegerMax) return NULL; if (indexes != NULL) { *(indexes - 1) = i; return (indexes - 1); } } }

  (*count)–; return NULL; }

@end

– MiloBird