Could not cast value of type 'UITabBarController' to 'ViewController'

问题

The situation: when I press a button in rentViewController, it pops up a tableviewcontroller. If a specific cell has been pressed, it sends data to rentViewController. In order to send data from one view controller to another I needed the code

let rentViewController : RentViewController = self.presentingViewController as! RentViewController <- here is where the error shows up

so that tableviewcontroller could get access to the variables and functions from rentviewcontroller. I'm using

self.dismiss(animated: true, completion: nil)

to get out of the tableviewcontroller and back to the rentviewcontroller. However, it gives me an error "Could not cast value of type 'UITabBarController' to 'RentViewController'". I did some research and I think it's according to the orders of my view controllers but I'm not sure how to change it in a way that it works. My initial view is 'TabBarController' and the order after that is 'NavigationController' -> 'RentViewController' -> 'TableViewController'. If you have questions feel free to ask I can provide you more information.

回答1:

Your viewController is being presented from UITabBarController. With approach you are using I believe you can access it like this (where index is index in UITabBarController of your UINavigationController containing RentVC):

if let tab = self.presentingViewController as? UITabBarController, 
    let nav = tab.viewControllers?[index] as? UINavigationController,     
    let rentViewController = nav.viewControllers.first as? RentViewController {

        rentViewController.data = data
}

However, I would suggest using a delegate or callback block to pass data in this occassion.

For delegate approach, first create protocol:

protocol PassDataDelegate:class {
    func passData(data:YourType)
}

Then in TableViewController:

class TableViewController: UIViewController {
    weak var delegate: PassDataDelegate?
}

And in RentViewController:

extension RentViewController: PassDataDelegate {
    func passData(data:YourType) {
        //use data to suit your needs
    }
}

Before presenting TableViewController, in RentViewController, set its delegate:

tableViewController.delegate
present(tableViewController, animated: true)

And finally, inside TableViewController, before dismissing, call delegate's method to pass data:

delegate?.passData(data: <<someData>>)

来源：https://stackoverflow.com/questions/47480327/could-not-cast-value-of-type-uitabbarcontroller-to-viewcontroller

标签

ios

swift

uinavigationcontroller

uitabbarcontroller