passing data back using delegation & storyboards

Question

I am having some issues getting the hang of using delegates with Storyboards in an app I'm working on. I've reviewed some other searches, including Passing data back :Delegate method not called, but to no avail. At this point, I've deleted everything in my app, except for the the basics of my two views. The first view is a basic view controller with a button that when pushed, segues to a modal view, where one pice of data is entered in a textfield. A Save button is on that modal view, that when pushed, returns back to the first view. Of course, I want to send that entered data back to the first view as well. Sounds simple? Sure, but somewhere I can't get it to work. It seems my delegate call is never made. Here's the code:

MyDayViewController.h - this is the first view controller

#import <UIKit/UIKit.h>
#import "AddRatingModalViewController.h"

@interface MyDayViewController : UIViewController <AddRatingDelegate>

@property (strong, nonatomic) IBOutlet UIButton *addRatingBtn;
@property (strong, nonatomic) IBOutlet UIButton *addAccompBtn;
@property (strong, nonatomic) IBOutlet UILabel *ratingLabel;

@end

MyDayViewController.m

#import "MyDayViewController.h"

@implementation MyDayViewController
@synthesize addRatingBtn;
@synthesize addAccompBtn;
@synthesize ratingLabel;

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:@"ToRatingVC"])
{
    NSLog(@"Setting MyDayVC as a delegate of AddRatingMVC");

    AddRatingModalViewController *addRatingController = segue.destinationViewController;
    addRatingController.delegate = self;
}
}

- (void)theSaveButtonTapped:(AddRatingModalViewController *)controller withRating:(NSNumber*) rating
{
NSLog(@"In theSaveButtonTapped method of MyDayVC");
ratingLabel.text = [[NSString alloc]initWithFormat:@"%@", rating];

[self dismissModalViewControllerAnimated:YES];
}

- (void)viewDidUnload
{
[self setAddRatingBtn:nil];
[self setAddAccompBtn:nil];
[self setRatingLabel:nil];
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}

@end

AddRatingModalViewController.h - this is the modal view controller

#import <UIKit/UIKit.h>

@class AddRatingModalViewController;

@protocol AddRatingDelegate
- (void)theSaveButtonTapped:(AddRatingModalViewController *)controller withRating:(NSNumber*) rating;
@end

@interface AddRatingModalViewController : UIViewController

@property (nonatomic, weak) id <AddRatingDelegate> delegate;
@property (strong, nonatomic) IBOutlet UITextField *addRatingTextField;

- (IBAction)cancelBtnPressed:(id)sender;
- (IBAction)saveBtnPressed:(id)sender;

@end

AddRatingModalViewController.m

#import "AddRatingModalViewController.h"

@implementation AddRatingModalViewController
@synthesize addRatingTextField;
@synthesize delegate;

- (IBAction)cancelBtnPressed:(id)sender {
[self dismissModalViewControllerAnimated:YES];
}

- (IBAction)saveBtnPressed:(id)sender {
NSNumber *ratingARMVC = [NSNumber numberWithInteger:[addRatingTextField.text integerValue]];
NSLog(@"The entered Rating in ARMVC is %@", ratingARMVC);

NSLog(@"Telling the MyDayVC Delegate that Save was tapped on the AddRatingTVC");
[self.delegate theSaveButtonTapped:self withRating:ratingARMVC];

}

- (void)viewDidUnload
{
[self setAddRatingTextField:nil];
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}

@end

Output from the console is as such:

2012-07-16 16:49:16.384 MyDayDelTest[4695:f803] Setting MyDayVC as a delegate of AddRatingMVC
2012-07-16 16:49:39.274 MyDayDelTest[4695:f803] The entered Rating in ARMVC is 7
2012-07-16 16:49:39.275 MyDayDelTest[4695:f803] Telling the MyDayVC Delegate that Save was tapped on the AddRatingTVC

This is right before the delegate call is supposed to be made in the Save method. Any help would be greatly appreciated! I should say that tests work when I don't use storyboards, but I do need this to work with Storyboards, as the rest of my app uses them. Thanks in advance.

Answer 1

@pina0004 discovered an answer here. In summary, if the pushed VC is really the root VC of a UINavigationController, the segue destinationViewController won't point to the pushed VC, but rather (less intuitively) to the nav controller in which it's the root.

That's solved, but I think this is an example of overuse of the delegate pattern. In this case, the pushed VC needs to report a string back to the original, and the question uses a delegate pointer to the original, who's only "delegated" work is to save the string and dismiss the modal VC. I think there are better alternatives:

• Pass the model: instead of telling the pushed VC who the pushing VC is, give it a pointer to it's model (in this case, the string). Let the pushed VC change the model, and then use one of several techniques for the pusher to discover the model has changed.
• Dismiss itself: it's not very evident from the way the methods are named, but a modally presented VC can dismiss itself. The pushing VC can check the model state in it's viewWillAppear method, which will run as the pushed VC is about to disappear.
• KVO: The original VC can ask to be notified when a specific model property changes. This will let the pushing find out about a model state change, and dismiss the modal VC if it wants.
• Notification: either the pushed VC or the model can post notification of state changes. The pushing VC can subscribe to this and respond. This is especially helpful for state changes that may be of more general interest to the app.
• Blocks: The pushing VC can use blocks to hand over some code that should run when something important happens. The block runs in the context of the pushing VC. This is a very readable way to keep the cause-and-effect blocks of code near each other, even sharing the same variable names.