Implementing UITabBarControllerDelegate does not work

Question

I have created a new class to implement UITabBarControllerDelegate, but the method in the class does not been invoked.

AppDelegate.swift:

func application() {
  // ...

  let controller = MyTabItemController()
  let tabBarController = UITabBarController()
  tabBarController.viewControllers = [controller]
  tabBarController.delegate = MyTabBarControllerDelegate()

  self.window?.rootViewController = tabBarController

  // ...
}

MyTabBarControllerDelegate.swift:

class MyTabBarControllerDelegate: NSObject, UITabBarControllerDelegate{
  func tabBarController(/*...*/) {
    print("method invoked")
  }
}

When I selected the item, the message "method invoked" is not shown.

If I let AppDelegate extend UITabBarControllerDelegate, everything worked well and the message is shown in console.

I want to know why this happened?

Any particular reason for creating a separate class for tabbarController delegate ? — Nitish
– Nitish, Commented Feb 26, 2018 at 7:23

clemens · Accepted Answer · 2018-02-26 07:28:19Z

1

The delegate property of UITabBarController is weak. Thus, your delegate is released directly after the assignment. You should keep you delegate object by a strong reference.

answered Feb 26, 2018 at 7:28

clemens

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