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];
}

score 6 · Accepted Answer · answered Feb 20 '12 at 11:24

[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

Would you suggest saving the UIVIewController in AppDelegate for a global solution? — Dejell, Dec 27 '12 at 12:55
@Odelya I would always advise that you avoid clogging up your app delegate with application-wide variables. Better to use singleton instances or some form of manager class. — Ell Neal, Dec 28 '12 at 01:05

0xSina · Answer 2 · 2012-02-20T11:14:08.613

0

In order for setValue:ForKey: to work, your view controller must conform to NSKeyValueCoding protocol.

Try this:

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

and don't forget to retain/release appropriately in your setFoo: method. You probably also need to type cast parentViewController to avoid any warnings.

edited Feb 20 '12 at 11:14

answered Feb 20 '12 at 11:01

0xSina

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This won't work in iOS 5, `[UIViewController parentViewController]` has a different meaning in iOS 5 so you should use `[UIViewController presentingViewController]` if this is the case. – Ell Neal Feb 20 '12 at 11:16

score 0 · Answer 3 · answered Feb 20 '12 at 11:25

0

Pass the reference of the master with assign property to detail view. Using this reference set the foo value before performing pop action.

answered Feb 20 '12 at 11:25

Apurv

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score 0 · Answer 4 · answered Feb 20 '12 at 11:36

gIf you want to pass a object to the parent you could try creating an external object in a header file and importing the header in the controller where you want to use it however THIS IS NOT BEST PRACTICE but it's a quick fix import

extern MyObject* Object;
@interface GlobalVariables : NSObject {

}

@end

All you have to do now is include the header in the controllers and use the global variable.

If you want to do it by the books i suggest you create a delegate that handles the object passing.

score 0 · Answer 5 · edited May 23 '17 at 11:56

0

Normally, under this scenario, you need to use delegate. Check out my answer to this similar question in this SO.

edited May 23 '17 at 11:56

Community

1
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answered Feb 20 '12 at 15:08

user523234

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Unable to pass value back to parentViewController

5 Answers5