segue: destination view controller weirdness

Question

In my app, I use a storyboard and segues, and I often pass data to the destination view controller before doing the segue, as follows:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender 
{
    if ([segue.destinationViewController respondsToSelector:@selector(setMyData:)]) {
        [segue.destinationViewController performSelector:@selector(setMyData:) 
                                          withObject:myData];
    }
} 

It works everywhere except in one place. The selector gets called, the data gets set, but when the segue completes and the destination controller appears, it doesn't have the data I just set. After printing the view controller's id in both the source and destination view controllers, I found that the segue.destinationViewController in the code above is a DIFFERENT instance of the view controller than the one that gets displayed. What's going on here?

[UPDATE 1] I looked into the lifecycle of the destination view controller, and it first gets loaded during the segue execution, but AFTER I set the property on it! This means, that when I call performSelector on it, the view controller object is not initialized! This is why the data I set doesn't stick. t don't understand why is this the case, and why this same approach works in the other parts of my app.

[UPDATE 2] Posting the code of setMyData by request. At first I didn't have this method at all, because locationToOpen is a public property. I only added it to ensure it gets called and to print the debug info.

- (void)setMyData:(MyData *)myData
{
    DLog(@"self: %@", (id)self);
    _myData = myData;
}

Answer 1

I had this same issue. It turned out for me that the target ViewController property I was setting in my prepareForSegue: code was declared as weak because I had copied and pasted the property from one that InterfaceBuilder auto-created, but mine was not a Storyboard object. So my property was being released and zeroed by ARC on exit from prepareForSegue:. Making it a non-weak property fixed it.

Answer 2

I had a similar problem where the ViewController I was doing the segue to changed at some odd point, after a looking around a bit it seems that the segue created a new ViewController.

To solve the data passing problem I used notifications.

Answer 3

I know this thread is old and solution should be found. But since the final solution is not posted here, I would like to list one of the possible root cause (which is the one in my case). I had the same issue, trying to set the variable in the destination view controller of the segue. The root cause is that I forgot to instantiated ([[Class alloc]init]) the object variable. I need it in my case because I am setting the properties of the object instead of pointing to other object. Hope this help.

Answer 4

I would do it as follows -

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender 
{
    if ([segue.identifier isEqualToString:@"NextSegue"]) 
    {
        DestinationViewController *dest = [segue destinationViewController];

        dest.myData = self.myData; 
    }
}

And in the DestinationViewController.h, you should create a property -

#import <UIKit/UIKit.h>

@interface DestinationViewController : UIViewController

@property (nonatomic, strong) NSObject *myData;


@end

And also, make sure to synthesize the myData property in DestinationViewController.m -

@interface DestinationViewController ()

@end

@implementation DestinationViewController

@synthesize myData = _myData;

// other methods here

@end