title: NSString isEqualToString - Unrecognized selector sent to instance
body: <p>Why do I get an Unrecognized Selector sent to instance at </p>
  
  <pre><code>doesExist = [myStr isEqualToString:@"Hello"];
  
  - (void) centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI
  {
  
      NSLog(@"%s", __PRETTY_FUNCTION__);
      NSLog(@"Found %d peripheral as a result of scanning", myListOfPeripherals.count);
  
      NSString *strMACId = [advertisementData valueForKey:@"kCBAdvDataManufacturerData"];
      NSLog(@"%@", strMACId);
  
  
  
      [timerConnectionTimeout invalidate];
      PeripheralCell * objPeripheralCell;
  
      NSLog(@"Found Peripheral with Name: %@ RSSI data:%@ AdvData: %@", peripheral.name, peripheral.RSSI, advertisementData);
  
      // Check if the Peripheral already exists in your collection - if no add it.
      if ([self peripheralExistsWithMacId:strMACId] == false)
      {
          // New peripheral - Add it to the list of myPeripherals
          objPeripheralCell=[[PeripheralCell alloc] init];
          [myListOfPeripherals addObject: objPeripheralCell];
          objPeripheralCell.peripheral=peripheral;
          objPeripheralCell.rssi=RSSI;
          objPeripheralCell.peripheralMacId = strMACId;
  
      }
  
  }
  
  
  
  
  -(BOOL) peripheralExistsWithMacId:(NSString *)strMacId
  {
      BOOL doesExist = false;
      for (int i=0; i&lt;myListOfPeripherals.count; i++)
      {
          PeripheralCell *objPeripheralCell = myListOfPeripherals[i];
          NSString *myStr = objPeripheralCell.peripheralMacId;
          NSLog(@"Comparing %@ with %@", myStr, strMacId);
          **doesExist = [myStr isEqualToString:@"Hello"];**
          if (doesExist)
          {
              break;
          }
      }
      return doesExist;
  
  }
  </code></pre>
  
  <p>Error -->>  <code>-[NSConcreteData isEqualToString:]: unrecognized selector sent to instance 0x7970e90</code></p>
  
  <p>Update:
   NSLog(@"%@", strMACId) yields &lt;00ff6e62 61bacad8>  How can I tell that this is not a NSString Object</p>