Obj-C wrapper and categories for NSString and NSURL for Cocoa UTTypes

Foundation+NSUTType.h

#import <Foundation/Foundation.h>

typedef NS_ENUM(NSUInteger, NSUTType) {
  NSUTTypeImage,
  NSUTTypeMovie,
  NSUTTypeAudio,
  NSUTTypeUnknown
};

@interface NSURL (UTType)
- (NSUTType) UTType;
@end

@interface NSString (UTType)
- (NSUTType) UTType;
@end

Foundation+NSUTType.m

#import "Foundation+UTType.h"

@implementation NSURL (UTType)
- (NSUTType) UTType { return self.absoluteString.UTType; }
@end

@implementation NSString (UTType)

- (NSUTType) UTType {
  CFStringRef UTI = UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension,
                                                          (__bridge CFStringRef)(self.pathExtension),
                                                          NULL);
  static NSDictionary *map = nil;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    map = @{
            (id) kUTTypeImage : @(NSUTTypeImage),
            (id) kUTTypeMovie : @(NSUTTypeMovie),
            (id) kUTTypeAudio : @(NSUTTypeAudio)
            };
  });

  NSUTType ret = NSUTTypeUnknown;
  for (NSString *type in map.allKeys) {
    if (UTTypeConformsTo(UTI, (__bridge CFStringRef)(type))) {
      ret = [map[type] integerValue];
    }
  }

  CFRelease(UTI);
  return ret;
}

@end

TODO: expand to more types/subtypes