Why is there a compiler warning on this statement?

Question

In a standard iPhone app I'm displaying an image picker on top of a table view. The code works fine (I believe ;-)), but I get a compiler warning when setting the image picker delegate to be the table view controller (ChoiceController).
ChoiceController is defined to implement the delegate:

@interface ChoiceController : UITableViewController <UIActionSheetDelegate, UIImagePickerControllerDelegate, MFMailComposeViewControllerDelegate> and clearly does become the delegate, because it receives all the appropriate actions.

I've tried casting ChoiceController, ie self, to UIImagePickerControllerDelegate but I get the same result.

Insights welcomed!

Answer 1

You can see in the warning text that the delegate has to be UIImagePickerControllerDelegate , but also UINavigationControllerDelegate .

It's defined so: @property (nonatomic, assign) id<UINavigationControllerDelegate, UIImagePickerControllerDelegate> delegate

In your case, it works fine because all UINavigationControllerDelegate methods are optional. Had that not been the case, the app would have crashed with unknown selector send to instance exception.

You should implement the UINavigationControllerDelegate protocol. If you do not need any of the methods declared there, and they are indeed optional, do not implement them.