Why Xcode shows warning when use AVAudioPlayer Delegate protocol in appdelegate.h file?

Question

//---------MyAppDelegate.h

@interface MyAppDelegate : NSObject <UIApplicationDelegate, AVAudioPlayerDelegate> {

//---in some other .m file, trying to acess the device token residing in MyAppDelegate ----------

MyAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

// Results in // warning: type 'id ' does not conform to the 'AVAudioPlayerDelegate' protocol

Answer 1

It is because of a type mismatch: - The UIApplication.delegate property returns an instance of type id - You are trying to cast this instance into MyAppDelegate which implements the UIApplicationDelegate and the AVAudioPlayerDelegate protocols. - As the type returned by the delegate property does not match the appDelegate type, you see the warning.