Unable to pass value back to parentViewController

Question

I have masterViewController and detailViewController. Masterview pushes detailView. When going back to masteViewController I want to update the foo value. But I only get NULL from nslog. How can I set the parenteViewContrller.foo value to @"bar" when navigationback?

masterViewController.h

    NSString *foo; 
    -(void)setFoo:(NSString *)fooValue
    @property(nonatomic, retain) NSString *foo; 

masterViewController.m

@synthesize foo;

-(void)setFoo:(NSString *)fooValue{

    NSLog(@"updated foo:%@", fooValue);
}

detailViewController.m

-(void)goBack{
    [self.navigationController.parentViewController setValue:@"bar" forKey:@"foo"];
    [self.navigationController popViewControllerAnimated:YES];
}

Answer 1

[UIViewController parentViewController] will not return what you are expecting from iOS 5 onward, instead you should be using [UIViewController presentingViewController]

If you are just targeting iOS 5, it is easy enough to start using presentingViewController instead, but if not I would advise that you manually pass your UIViewController on:

// DetailViewController.h

@class MasterViewController;

@interface DetailViewController : UIViewController

@property (assign, nonatomic) MasterViewController *masterViewController;

@end


// DetailViewController.m

#import "DetailViewController.h"
#import "MasterViewController.h"

@implementation DetailViewController

- (void)goBack {

    [self.masterViewController setFoo:@"bar"];

    // dismiss this view controller
}

@end


// MasterViewController.h

@interface MasterViewController : UIViewController

- (void)setFoo:(NSString *)bar;

@end


// MasterViewController.m

#import "MasterViewController.h"
#import "DetailViewController.h"

@implementation MasterViewController

- (void)goForward {

    DetailViewController *detailViewController = ...;
    [detailViewController setMasterViewController:self];

    // present this view controller
}

@end