Question

MPPopoverControllerDelegate.h file

#import <Foundation/Foundation.h>
@class MPPopoverController;

@protocol MPPopoverControllerDelegate <NSObject>    
@optional
- (void)popoverControllerDidDismissPopover:(MPPopoverController *)popoverController;
@end

MPPopoverController.h file

#import <UIKit/UIKit.h>

@protocol MPPopoverControllerDelegate;

@interface MPPopoverController : UIViewController <MPPopoverControllerDelegate>

@property (nonatomic, assign) id<MPPopoverControllerDelegate> delegate;

@end

MPPopoverController.m file

#import "MPPopoverController.h"
#import "MPPopoverControllerDelegate.h"

@implementation MPPopoverController
@end

@property (nonatomic, assign) id<MPPopoverControllerDelegate> delegate; : this line has warning

Cannot find protocol definition for ‘MPPopoverControllerDelegate’

What is wrong? And how to fix this warning?
if replace ‘@protocol MPPopoverControllerDelegate’; with ‘#import “MPPopoverControllerDelegate.h’, everything will be ok.
But link – in Referring to Other Protocols you can see that apple says to use @protocol

Answer 1

Is there an absolute need for your protocol declaration to be in a different header file? Unless it’s quite a large protocol definition (which yours isn’t), I would suggest declaring it below your interface declaration.

MPPopoverController.h

#import <UIKit/UIKit.h>

@protocol MPPopoverControllerDelegate;

@interface MPPopoverController : UIViewController

@property (nonatomic, assign) id<MPPopoverControllerDelegate> delegate;

@end


@protocol MPPopoverControllerDelegate <NSObject>    
@optional
- (void)popoverControllerDidDismissPopover:(MPPopoverController *)popoverController;
@end