Obj-C protocol oriented approach

#import <UIKit/UIKit.h>

typedef void (^MSTDismissCallback)(void);

@protocol MSTDismissWithCallbackProtocol <NSObject>

@optional
@property (nonatomic, copy) MSTDismissCallback dismissCallback;
- (void) injectCallback:(MSTDismissCallback) dismissCallback;
- (void) dismissViewControllerWithCallback;

@end

@interface UIViewController (DismissCallback) <MSTDismissWithCallbackProtocol>

@property (nonatomic, copy) MSTDismissCallback dismissCallback;

- (void) injectCallback:(MSTDismissCallback) dismissCallback;
- (void) dismissViewControllerWithCallback;

@end

@implementation UIViewController (DismissCallback)

@dynamic dismissCallback;

- (void) injectCallback:(MSTDismissCallback) dismissCallback {
  self.dismissCallback = dismissCallback;
}

- (void) dismissViewControllerWithCallback {
  od_weakify(self)
  [self dismissViewControllerAnimated:true completion:^{
    od_strongify(self)
    if (self.dismissCallback != nil) {
      self.dismissCallback();
    }
  }];
}

@end