Swift-从标签栏控制器更新视图控制器内的变量

Question

I need to update a variable in a View Controller and I need to do that from a Tab Bar Controller.

See image below:

I have tried so many different code but, since i implemented a Navigation Controller in between, none of them is working.

Code1

let myVC:MyViewController = self.viewControllers?[0] as MyViewController
myVC.x = "marco"

Code2

var storyboard : UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
var myVC:MyViewController = storyboard.instantiateViewControllerWithIdentifier("view2") as MyViewController
myVC.x = "marco"

Code3

let myInstance:MyViewController = MyViewController()
myInstance.x = "marco"

But none of them is working. Help please

Thank you very much

Answer 1

You need to follow the view controller hierarchy from your tab bar controller down to your custom view controller, like this:

Tab bar controller (self) -> navigation controller -> custom view controller

We want to get the tab bar controller's first view controller (a navigation controller), and then get that navigation controller's first view controller. In code, you can do it this way:

let myVC = (self.viewControllers?[0] as UINavigationController).viewControllers[0] as MyViewController
myVC.x = "marco"

Note that this is brittle, and will fail if you change the hierarchy at all.