title: iOS 10 : How can I get a call event using CallKit/CXCallObserver?
body: <p>I changed the CTCallCenter with CXCallObserver in iOS 10.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>#import &lt;CallKit/CXCallObserver.h&gt;
  #import &lt;CallKit/CXCall.h&gt;
  
  -(void)viewDidLoad {
  
      CXCallObserver *callObserver = [[CXCallObserver alloc] init];
      [callObserver setDelegate:self queue:nil];
  
      ... ...
  }
  
  - (void)callObserver:(CXCallObserver *)callObserver callChanged:(CXCall *)call {
      if (call.hasConnected) {
          NSLog(@"********** voice call connected **********/n");        
      } else if(call.hasEnded) {
          NSLog(@"********** voice call disconnected **********/n");        
      }
  }
  </code></pre>
  
  <p>But I can't get a voice call event and I got a warning like this:</p>
  
  <pre><code>Sending 'HomeViewController *const __strong' to parameter of incompatible type 'id&lt;CXCallObserverDelegate&gt; _Nullable
  </code></pre>
  
  <p>Please help me.</p>