UITabbarのバッジを色んなところからアクセス

swift

self.tabBarController?.tabBar.items![0].badgeValue = "New" // 0番目のタブにNew

swift

override func tabBar(tabBar: UITabBar, didSelectItem item: UITabBarItem!) {
     self.tabBar.items![0].badgeValue = "New"
}

swift

for i in 0..<5 {
    let tabItems = self.tabBar.items! as [UITabBarItem]
    tabItems[i].badgeValue = "New"
}