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iOS

Posted by M T
M T
11,934 Points

Pass data between tab bar view controllers programmatically

Unfortunately, didSelectViewController is only called when a user physically taps on a tab. If you switch tabs programmatically, the method is not called.

I'm trying to accomplish something similar to what would be done in a prepareForSegue method, where a property of the destination view controller is set prior to loading the view.

My attempt at passing values compiles, but I get a SIGABRT error "unrecognized selector sent to instance" for the value I set. After I hit a button, here's how I make my attempt in the function:

    MyVC *destView = (MyVC *)[self.tabBarController.viewControllers objectAtIndex:2]; //get destination viewController
    destView.item = self.item; //share item between viewControllers
    [self.tabBarController setSelectedViewController:destView]; //change View

Or I could do [self.tabBarController setSelectedIndex:2]; for the last line.

Bummed this attempt didn't work. When I wrote something that didn't result in errors, I thought I was home free.

The property is set to nonatomic, strong.

Each solution seems just a step away from working. Thoughts?

M T
M T
11,934 Points

Update: it appears the class to tabBarController.viewControllers isn't a view controller, but a NavigationController. That's what is causing the "unrecognized selector set to instance" error.

M T
M T
11,934 Points

Update: To get the view controller from the navigation controller, use topViewController like so:

UIViewController *destView = [[self.tabBarController.viewControllers objectAtIndex:2] topViewController];

However, if you check [destView class] isKindOfClass: [MyVC class] they will not equate even though if you log each of those independently you get "MyVC". No error will happen, it just won't pass the value.

Getting closer.

1 Answer

M T
M T
11,934 Points
M T
M T
11,934 Points

And answer: To check the class, use don't use [destView class], just use destView. And then everything works as hoped.

if ([destView isKindOfClass:[MyVC class]])
{
MyVC destinationViewController = (MyVC *)destView;
destinationViewController.item = self.item;
}