title: Undefined symbols for architecture i386: "_OBJC_CLASS_$_Barcode", referenced from: objc-class-ref in
body: <p>I am trying to integrate a QR code generating library in to my App. </p>
  
  <p>the QR generator library is:</p>
  
  <p><a href="https://github.com/kuapay/iOS-QR-Code-Generator" rel="nofollow">https://github.com/kuapay/iOS-QR-Code-Generator</a></p>
  
  <p>I guess I must have integrated it wrong as I am getting this error:</p>
  
  <pre><code>Undefined symbols for architecture i386:
    "_OBJC_CLASS_$_Barcode", referenced from:
        objc-class-ref in QRViewController.o
  ld: symbol(s) not found for architecture i386
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>What is most likely to be causing this?</p>