NSArray *tabBarItems = self.tabBar.items;
UITabBarItem *personCenterTabBarItem = [tabBarItems objectAtIndex:3];
personCenterTabBarItem.badgeValue = [NSString stringWithFormat:@"%ld",num];
消除的时候
NSArray *tabBarItems = self.tabBar.items;
UITabBarItem *personCenterTabBarItem = [tabBarItems objectAtIndex:3];
personCenterTabBarItem.badgeValue = nil;