Detect when a tab bar item is pressed

problem ：

I have a root view controller which isn't set as the custom class for any of my view controllers on my storyboard. I have a root view controller , It is not set as a custom class for any view controller on my storyboard .Instead, all of my view controllers are subclassing this class like so. contrary , All my view controllers class this class like this .

// RootViewControllerclass RootViewController: UIViewController, UITabBarDelegate {     // This is not getting executed on any of the view controllers    func tabBar(tabBar: UITabBar, didSelectItem item: UITabBarItem) {        print("ddd")    }}// Subclassing it class TopStoriesViewController: RootViewController {}

But I seem to be struggling with doing something when a tabbaritem is pressed on the view controller which is subclassing the rootviewcontroller, ie, the message is not being printed. however , When inheriting rootviewcontroller Press tabbaritem when , I seem to be trying to do something , That is, no message is printed .

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Solution ：

Reference resources ： https://stackoom.com/en/question/2Hyfj