To avoid this warning, you will need to make sure that when using the Chartboost method
[Chartboost startWithAppId:@"..." appSignature:@"..." delegate:self] the class of the object you're passing in as the delegate conforms to the
Check your AppDelegate.h file and make sure the interface contains the proper delegate references:
@interface AppDelegate : UIResponder <UIApplicationDelegate, ChartboostDelegate>
You can refer to the "Conforming to Protocols" section of Apple's documentation for a more detailed explanation.