title: how do I declare facebookSDK in ios?
body: <p>I'm trying to make a log in with facebook but I keep getting a error message, " Use of undeclared identifier "<code>FBSDKApplicationDelegate</code>" does anyone know how should I do it. </p>
  
  <pre><code>#import "AppDelegate.h"
  #import "FacebookSDK.h"
  #import &lt;Parse/Parse.h&gt;
  #import &lt;ParseFacebookUtils/PFFacebookUtils.h&gt;
  #import &lt;FacebookSDK.h&gt;
  
  @interface AppDelegate ()
  
  @end
  
  
  @implementation AppDelegate
  
  - (BOOL)application:(UIApplication *)application    didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
  {
  [Parse setApplicationId:@"xxxxxxxxxxxxxxxxxxxx"
                clientKey:@"xxxxxxxxxxxxxxxxxxxx"];
  [PFAnalytics trackAppOpenedWithLaunchOptions:launchOptions];
  [PFFacebookUtils initializeFacebook];
  
  return [[FBSDKApplicationDelegate sharedInstance] application:application
                                  didFinishLaunchingWithOptions:launchOptions];
  }
  </code></pre>