title: Undefined symbols for architecture arm64: "_OBJC_CLASS_$_PayTabCardReaderViewController", referenced from: objc-class-ref in ViewController.o
body: <p>I am getting this weird error when importing a library called pay tabs </p>
  
  <pre><code>Undefined symbols for architecture arm64:
  "_OBJC_CLASS_$_PayTabCardReaderViewController", referenced from:
    objc-class-ref in ViewController.o
  ld: symbol(s) not found for architecture arm64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>Under build settings</p>
  
  <p>Architectures: </p>
  
  <p>Architecture Standard architectures (armv7, arm64) - $(ARCHS_STANDARD)
  Base SDK Latest IOS(8.4)</p>
  
  <p>Build Active Architecture Only 
  Debug Yes
  Release No</p>
  
  <p>Supported Platforms IOS
  Valid Architectures armv7 arm64</p>