The Core iOS Developer’s Cookbook, Fifth Edition

Moving from UTI to Extension or MIME Type

To go the other way, producing a preferred extension or MIME types from a UTI, use UTTypeCopyPreferredTagWithClass(). The following functions return jpeg and image/jpeg, respectively, when passed public.jpeg:

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NSString *extensionForUTI(NSString *aUTI) {     CFStringRef theUTI = (__bridge CFStringRef) aUTI;     CFStringRef results =         UTTypeCopyPreferredTagWithClass(             theUTI, kUTTagClassFilenameExtension);     return (__bridge_transfer NSString *)results; } NSString *mimeTypeForUTI(NSString *aUTI) {     CFStringRef theUTI = (__bridge CFStringRef) aUTI;     CFStringRef results =         UTTypeCopyPreferredTagWithClass(             theUTI, kUTTagClassMIMEType); ...