title: iOS didSelectTabBarItem knowing what item was selected prior
body: <p>I have an IOS app with a <code>UITabBar</code> and have its delegate set to my class.. the <code>didSelectTabBarItem</code> properly fires and all is right with the world. However I do have some conditional code that has to occur when the <code>UITabBarItem</code> selected is after one particular <code>UITabBarItem</code> IE.. if the user clicks on tab bar item 3, and they were currently on tab bar item 2 I have to do a little extra code, that I would not have to do if the user selected tab bar item 3 and was previously on tab bar item 1. </p>
  
  <p>So, is there anyway programmatically (other than keeping direct track via my program via a state variable, to know what was the previously selected item was on a tab bar when a new tab bar item is selected?</p>