title: vtable for .. referenced from compile error xcode
body: <p>I was getting the following error compiling an iPhone project:</p>
  
  <pre><code>"vtable for oned::MultiFormatUPCEANReader", referenced from:
        __ZTVN4oned23MultiFormatUPCEANReaderE$non_lazy_ptr in MultiFormatUPCEANReader.o
  ld: symbol(s) not found
  collect2: ld returned 1 exit status
  </code></pre>
  
  <p>Anybody know how I may fix it?</p>