title: How to resolve the ONLY_ACTIVE_ARCH=YES error in Xcode 6?
body: <p>I am running a project in Xcode 6 ,I am facing this error can any one help to resolve the issue . I has changed valid architecture to <code>armv7 armv7s arm64</code>    then the issue not shown again , but i was getting other error for file while is not support for 64 bit. I am getting below errors</p>
  
  <pre><code> "_OBJC_CLASS_$_OAAsynchronousDataFetcher", referenced from:
        objc-class-ref in LoginViewController.o
    "_OBJC_CLASS_$_OAConsumer", referenced from:
        objc-class-ref in SA_OAuthTwitterEngine.o
        objc-class-ref in LoginViewController.o
    "_OBJC_CLASS_$_OADataFetcher", referenced from:
        objc-class-ref in SA_OAuthTwitterEngine.o
    "_OBJC_CLASS_$_OAMutableURLRequest", referenced from:
        objc-class-ref in SA_OAuthTwitterEngine.o
        objc-class-ref in LoginViewController.o
    "_OBJC_CLASS_$_OARequestParameter", referenced from:
        objc-class-ref in SA_OAuthTwitterEngine.o
        objc-class-ref in LoginViewController.o
    "_OBJC_CLASS_$_OAToken", referenced from:
        objc-class-ref in SA_OAuthTwitterEngine.o
  ld: symbol(s) not found for architecture x86_64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  
  
  
  No architectures to compile for (ONLY_ACTIVE_ARCH=YES, active arch=x86_64, VALID_ARCHS=i386).
  </code></pre>
  
  <p>Waiting for response.</p>