#import <UIKit/UIKit.h>

@protocol NBNPhotoChooserViewControllerDelegate;

@interface NBNPhotoChooserViewController : UIViewController

- (instancetype)initWithDelegate:(id<NBNPhotoChooserViewControllerDelegate>)delegate;
- (instancetype)initWithDelegate:(id<NBNPhotoChooserViewControllerDelegate>)delegate
                     maxCellWidth:(CGFloat)maxCellWidth
                     cellSpacing:(CGFloat)cellSpacing;

@property (nonatomic) NSString *navigationBarTitle;
@property (nonatomic) NSString *cancelButtonTitle;
@property (nonatomic) BOOL shouldAnimateImagePickerTransition;

@end

@protocol NBNPhotoChooserViewControllerDelegate <NSObject>

- (void)photoChooserController:(NBNPhotoChooserViewController *)photoChooser didChooseImage:(UIImage *)image;

@optional
- (void)photoChooserDidCancel:(NBNPhotoChooserViewController *)photoChooser;

@end

#import <UIKit/UIKit.h>

@protocol NBNPhotoChooserViewControllerDelegate;

@interface NBNPhotoChooserViewController : UIViewController

- (instancetype)initWithDelegate:(id<NBNPhotoChooserViewControllerDelegate>)delegate;
- (instancetype)initWithDelegate:(id<NBNPhotoChooserViewControllerDelegate>)delegate
                     maxCellWidth:(CGFloat)maxCellWidth
                     cellSpacing:(CGFloat)cellSpacing;

@property (nonatomic) NSString *navigationBarTitle;
@property (nonatomic) NSString *cancelButtonTitle;
@property (nonatomic) BOOL shouldAnimateImagePickerTransition;

@end

@protocol NBNPhotoChooserViewControllerDelegate <NSObject>

- (void)photoChooserController:(NBNPhotoChooserViewController *)photoChooser didChooseImage:(UIImage *)image;
- (void)photoChooserDidCancel:(NBNPhotoChooserViewController *)photoChooser;

@end

--- 
+++ 
@@ -18,6 +18,8 @@
 @protocol NBNPhotoChooserViewControllerDelegate <NSObject>
 
 - (void)photoChooserController:(NBNPhotoChooserViewController *)photoChooser didChooseImage:(UIImage *)image;
+
+@optional
 - (void)photoChooserDidCancel:(NBNPhotoChooserViewController *)photoChooser;
 
 @end
Make delegate method optional (cancellation is handled automatically when using UINavigationController)
