How to read value for key with address in Xcode
===

My app crash and gives the output 
`value for key devices of object 0xde8a470 is nil` and "devices" (NSMutableArray) is set like this:


    - (void) centralManager:(CBCentralManager *)central 
    didDiscoverPeripheral:(CBPeripheral *)peripheral 
      advertisementData:(NSDictionary *)advertisementData 
                   RSSI:(NSNumber *)RSSI 
    {
     NSMutableArray *peripherals = [self mutableArrayValueForKey:@"devices"];
        if( ![self.devices containsObject:peripheral] )
            [peripherals addObject:peripheral];	 
    ...
    }

How can I know which object `0xde8a470` is and how can I read its value? 
