ObjectiveC NSArray map and compact

typedef id (^FnMapHandler)(id element, NSInteger index);

@interface NSArray (Functional)

- (NSArray *)fn_mapAndCompact:(FnMapHandler)mapHandler;
    
@end


@implementation NSArray (Functional)

- (NSArray *)fn_mapAndCompact:(FnMapHandler)mapHandler {
    NSAssert(mapHandler != nil, @"Must pass hander to map method");
    NSMutableArray *mutableCollection = [NSMutableArray array];
    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        id result = mapHandler(obj, idx);
        if (result != nil) {
            [mutableCollection addObject:result];
        }
    }];
    return [mutableCollection copy];
}

@end