title: Brain Tree Undefined symbols for architecture x86_64: "_OBJC_CLASS_$_Braintree"
body: <p>I am using Braintree in my app. But after getting token from my server and trying to initilise the Braintree object then it is showing the following error(i am using xCode v.7 and base SDK iOS 9.0 with PODS),</p>
  
  <pre><code>Undefined symbols for architecture x86_64:
    "_OBJC_CLASS_$_Braintree", referenced from:
        objc-class-ref in WZBrainTreeDemoViewController.o
  ld: symbol(s) not found for architecture x86_64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>When i remove this code it works but then it presents controller as nil,</p>
  
  <p>this is my code to initialise and present controller,</p>
  
  <pre><code>       strToken = dictResponse[@"braintree_client_token"];
  
  
           // If you haven't already, create and retain a `Braintree` instance with the client token.
           // Typically, you only need to do this once per session.
           self.braintree = [Braintree braintreeWithClientToken:strToken];
  
           // Create a BTDropInViewController
           BTDropInViewController *dropInViewController = [self.braintree dropInViewControllerWithDelegate:self];
           // This is where you might want to customize your Drop in. (See below.)
  
           // The way you present your BTDropInViewController instance is up to you.
           // In this example, we wrap it in a new, modally presented navigation controller:
           dropInViewController.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel
                                                                                                                 target:self
                                                                                                                 action:@selector(userDidCancelPayment)];
  
           UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:dropInViewController];
           [self presentViewController:navigationController animated:YES completion:nil];
  </code></pre>