prepareForSegue在模拟器上工作但不在设备上工作

Question

I am so tired of trying to make this work so i hope somebody here will be able to solve this for me..

I am using this code to segue to a UINavigationController. This code WORKS on simulator but NOT on a real device:

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    static NSString *segueIdentifier = @"ShowDetails";

    if ([[segue identifier] isEqualToString:segueIdentifier]) {

        NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

        UINavigationController *navigationController = segue.destinationViewController;
        DetailViewController *detailViewController = [navigationController viewControllers][0];


        detailViewController.selectedGameIdNumber = [NSString stringWithFormat: @"%ld", (long)indexPath.row];
        detailViewController.selectedSection = [self.sectionNames objectAtIndex:indexPath.section];
    }
}

On the real device it crashes at:

 DetailViewController *detailViewController = [navigationController viewControllers][0];

with the error:

-[DetailViewController viewControllers]: unrecognized selector sent to instance

Then i have this code that i tried. This code WORKS on device but NOT on simulator:

  -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    static NSString *segueIdentifier = @"ShowDetails";

    if ([[segue identifier] isEqualToString:segueIdentifier]) {

        NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

        DetailViewController * detailViewController = (DetailViewController *)segue.destinationViewController;


        detailViewController.selectedGameIdNumber = [NSString stringWithFormat: @"%ld", (long)indexPath.row];
        detailViewController.selectedSection = [self.sectionNames objectAtIndex:indexPath.section];
    }
}

On the simulator it crashes at:

detailViewController.selectedGameIdNumber = [NSString stringWithFormat: @"%ld", (long)indexPath.row];

With the error:

 -[UINavigationController setSelectedGameIdNumber:]: unrecognized selector sent to instance 0x7fa1d273e8

Am i doing something wrong or should i just run with the second code that works on real device? I want to have a clean solution so please do enlighten me if i am doing something wrong. Thank you all.

Answer 1

The issue is with how you are accessing the view controller. On the device the view controller hierarchy is different from on the simulator, and so the two solutions both only work in their own scenario. Of course it isn't the simulator that is different, but rather the device you are simulating (guess is iPad)

Be aware that, especially with splitViewcontrollers, but also with other framework provided view controllers that the functionality of the controllers may vary based on the target device. This change often bites you when you make assumptions about indexes of view controllers and the like.

Debug on the simulator, switching between device types and po the view controller and I think you will see what I mean.

Answer 2

Here's my solution: creating a generic struct and cast the customized viewcontroller by function call. The advantage is that you can reuse this function everywhere you need it. (Though my code is in written in swift rather than Objective-C, I think the way of solution is just alike)

struct DestinationController<T: UIViewController> {
    func get(segue: UIStoryboardSegue) -> T {
        if let navigation = segue.destinationViewController as? UINavigationController{
            return navigation.viewControllers.first as! T
        }
        return segue.destinationViewController as! T
    }
}