+ (NSData *)makeMeAData {
    dispatch_block_t dtor = DISPATCH_DATA_DESTRUCTOR_DEFAULT;
    
    dispatch_data_t data1 = dispatch_data_create("feliscatus", 10, nil, dtor);
    dispatch_data_t data2 = dispatch_data_create("isyour", 6, nil, dtor);
    dispatch_data_t data3 = dispatch_data_create("taxonomic", 9, nil, dtor);
    dispatch_data_t data4 = dispatch_data_create("nomenclature", 12, nil, dtor);
    dispatch_data_t data5 = dispatch_data_create_concat(
        dispatch_data_create_concat(dispatch_data_create_concat(data1, data2),
                                    data3), data4);
    
    return (NSData *)data5;
}

@end

import Foundation

let dispatchData = DataMaker.makeMeAData()
let nonDispatchData = "feliscatusisyourtaxonomicnomenclature".data(using: .ascii)!

print("enumerating dispatch data")
dispatchData[(dispatchData.startIndex + 5)...].enumerateBytes { ptr, idx, _ in
    print("idx: \(idx) slice: \(String(decoding: ptr, as: UTF8.self))")
}

print("enumerating non dispatch data")
nonDispatchData[(nonDispatchData.startIndex + 5)...].enumerateBytes { ptr, idx, _ in
    print("idx: \(idx) slice: \(String(decoding: ptr, as: UTF8.self))")
}

enumerating dispatch data
idx: 5 slice: catus
idx: 10 slice: isyour
idx: 16 slice: taxonomic
idx: 25 slice: nomenclature
enumerating non dispatch data
idx: 0 slice: catusisyourtaxonomicnomenclature