Some fun stuff for enumerating

NSArray+enumerableStuff.h

@interface NSArray (EnumerableStuff)
/**
 * similar to a map
 */
- (NSArray *) objectsTransformedByBlock:(id (^)(id, NSUInteger, BOOL *))block;

/**
 * filter the array
 */
- (NSArray *) objectsPassingTest:(BOOL (^)(id, NSUInteger, BOOL *))predicate;

/**
 * takes the return value of the block as the key and maps it to the object for it
 */

- (NSDictionary *) dictionaryOfObjectsWithKeyBlock:(id (^)(id, NSUInteger, BOOL *))block;
@end

NSArray+enumerableStuff.m

#import "NSArray+enumerableStuff.h"

@implementation NSArray (EnumerableStuff)

- (NSArray *) objectsTransformedByBlock:(id (^)(id, NSUInteger, BOOL *))block {
	NSMutableArray *ret = [NSMutableArray arrayWithCapacity:[self count]];
	
	[self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
		[ret addObject:block(obj, idx, stop)];
	}];
	
	return ret;
}


- (NSArray *) objectsPassingTest:(BOOL (^)(id, NSUInteger, BOOL *))predicate {
	return [self objectsAtIndexes:[self indexesOfObjectsPassingTest:predicate]];
}


- (NSDictionary *) dictionaryOfObjectsWithKeyBlock:(id (^)(id, NSUInteger, BOOL *))block {
	NSArray *keys = [self objectsTransformedByBlock:block];
	return [NSDictionary dictionaryWithObjects:self forKeys:keys];
}

@end