title: Possible way to detect sim card detection in ios?
body: <p>I have a iphone app that has the capability to send messages. I want to alert user when sim card is not available in iphone. So i tried below three function to check sim card availabilty</p>
  
  <pre><code>Class messageClass = (NSClassFromString(@"MFMessageComposeViewController"));
  if([messageClass canSendText]){
      // Sim available
      NSLog(@"Sim available");
  }
  else{
      //Sim not available
      NSLog(@"Sim not available");
  }
  
  if([MFMessageComposeViewController canSendText]){
      // Sim available
      NSLog(@"Sim available");
  }
  else{
      //Sim not available
      NSLog(@"Sim not available");
  }
  
  if([[UIDevice currentDevice].model isEqualToString:@"iPhone"])
  {
      if ([[UIApplication sharedApplication] canOpenURL:[NSURL URLWithString:@"tel:123456"]])
      {
          NSLog(@"Sim available");
      }
      else
      {
          NSLog(@"Sim not available");
      }
  }
  </code></pre>
  
  <p>I have checked my iphone without sim, it always return @"Sim available". But when i open default "Messages" app and try to send sms it says alert "No SIM Card Installed"... How this message app can detect sim card availabilty?</p>