Storyboard pass data backward from third VC to First VC

Question

My project has a design like this:

VC1 ---firstSegue----> VC2 ---secondSegue---> VC3

I have no problem in passing data backward from VC2 to VC1 and VC3 to VC2 by using protocol/delegate method. If I want to pass data from VC3 to VC1 directly, is it possible? OR should I insert a new segue from VC1 to VC3?

=================================== Update ======================================= My situation is when VC3 perform "-viewDidLoad", I want to ask VC1 to perform some action. After the action done, VC3 will continue to work.

Use Singleton data repository for data passing from one VC1 to VCn — Rajesh, Feb 18 '14 at 10:53
No, absolutely do not use a singleton. This is not what singletons are for. Doing this will only lead to pain in the future. Use Unwind Segues like @nkukushkin suggested. — Fogmeister, Feb 18 '14 at 11:33
But Unwind Segues must exit the third VC, right? What if I don't want to exit third VC? — user3322987, Feb 18 '14 at 11:50
I don't know the details of your implementation, but why would you want to pass data to first VC if you're not leaving the third one? — Nikita Kukushkin, Feb 18 '14 at 12:09
After VC1 performs some action, do you want it to pass some data to VC3? — Nikita Kukushkin, Feb 18 '14 at 12:15
@nkukushkin -- ask VC1 to perform some action together with some input data from VC3. (or maybe should i change my title?) — user3322987, Feb 19 '14 at 00:44
You should use `Unwind Segues`, you can find more info about them [in this question](http://stackoverflow.com/a/15839298/1607485). — Nikita Kukushkin, Feb 18 '14 at 10:54

bhavya kothari · Answer 1 · 2014-02-18T12:22:15.467

Option 1: Use NSUserDefaults to store and retrieve data

Step 1: For Storing

NSUserDefaults in VC3 view controller

[[NSUserDefaults standardUserDefaults] setObject:@"hello" forKey:@"mydata"];

Step 2: For Retrieving

NSUserDefaults in VC1 or any other controller:

NSString* receivedData = [[NSUserDefaults standardUserDefaults] objectForKey:@"mydata"];

Option 2: Using delegation and protocols

In VC3.h

@class VC3;

@protocol VC3Delegate <NSObject>
- (void)addItemViewController:(VC3 *)controller didFinishEnteringItem:(NSString *)item;
@end

@interface


@property (nonatomic, weak) id <VC3Delegate> delegate;

In VC3 we call a message on the delegate when we pop the view controller.

NSString *itemToPassBack = @"Pass this value back to VC1";
[self.delegate addItemViewController:self didFinishEnteringItem:itemToPassBack];

That's it for VC3. Now in VC1.h, tell VC1 to import VC3 and conform to its protocol.

#import "VC3.h"

@interface VC1 : UIViewController <VC3Delegate>

In VC1.m implement the following method from our protocol

- (void)addItemViewController:(VC3 *)controller didFinishEnteringItem:(NSString *)item
{
    NSLog(@"This was returned from VC3 %@",item);
}

The last thing we need to do is tell VC3 that VC1 is its delegate before we push VC3 on to nav stack.

NSMutableArray *arrayOfControllers = [[NSMutableArray alloc] initWithObjects:self.navigationController.viewControllers, nil];

  for (UIViewController *vc in arrayOfControllers) {
    if ([vc isKindOfClass:[VC3 class]]) {
        //It exists
           vc.delegate = self;
    }

Hi, I'm not pushing from VC1 to VC3 but from VC1 to VC2 to VC3. Then where should i put the "VC3.delegate=self"? — user3322987, Feb 18 '14 at 11:59
I thought we need to put VC3.delegate in "-(void)prepareForSegue:" ? — user3322987, Feb 18 '14 at 12:42

Storyboard pass data backward from third VC to First VC

1 Answers1