title: Change tab bar item badge from other ViewController
body: <p>I have a two tab bar items at the bottom of my application. (Let's call the tab bar items Products &amp; Cart)
  On Cart their is a badge item present. How can I change the badge item on Cart while I preform an action on the ViewController of Products.</p>
  
  <p>Steps:
  Start -> Cart badge = 0 -> go to Products tab -> add product to cart -> while adding product to cart change Cart badge to 1 -> still on the Products tab</p>