title: Other Linker Flags set to -ObjC
body: <p>I have included Other Linker Flags set to -ObjC in my Build Settings as I would like to use a framework that requires this (<a href="https://github.com/rs/SDWebImage" rel="nofollow">https://github.com/rs/SDWebImage</a>)</p>
  
  <p>However after adding this flag I get linker errors:</p>
  
  <pre><code>Undefined symbols for architecture armv7:
  </code></pre>
  
  <p>"_OBJC_CLASS_$_SKProductsRequest", referenced from:</p>
  
  <pre><code>  objc-class-ref in Parse(PFPurchase.o)
  </code></pre>
  
  <p>"_OBJC_CLASS_$_SKPayment", referenced from:</p>
  
  <pre><code>  objc-class-ref in Parse(PFPurchase.o)
  </code></pre>
  
  <p>"_OBJC_CLASS_$_SKPaymentQueue", referenced from:</p>
  
  <pre><code>  objc-class-ref in Parse(PFPurchase.o)
  
    objc-class-ref in Parse(PFPaymentTransactionObserver.o)
  </code></pre>
  
  <p>ld: symbol(s) not found for architecture armv7</p>
  
  <p>clang: error: linker command failed with exit code 1 (use -v to see invocation)</p>
  
  <p>Removing the -ObjC linker flag and the project builds again without errors. Any ideas of the cause? Thanks.</p>