title: Show an alert view when current location is near pin location
body: <p>I've the user current loaction, and the annotation pin location.
  When the user clicks on a button, the app starts to calculate the distance between the user current location and the pin location.
  This is my code:</p>
  
  <pre><code>- (IBAction)done:(id)sender {
  
  [Locate startUpdatingLocation];
  CLLocation *current;
  CLLocation *pin;
  do{
      current=[[CLLocation alloc]initWithLatitude:Locate.location.coordinate.latitude longitude:Locate.location.coordinate.longitude];
      pin=[[CLLocation alloc]initWithLatitude:arrived.latitude longitude:arrived.longitude];
  
  }while([current distanceFromLocation:pin]&gt;1000);
  
  }
  </code></pre>
  
  <p>The problem is, that when I click on this button (Done), it seems to enter an infinite loop and the app stops working.</p>