title: Remove last word in a string in Objective-c
body: <p>What is the most efficient way to split a string into two parts, in the following way</p>
  
  <p>One part is the last word of string that follows last whitespace character in the string
  Second part is rest of the string</p>
  
  <p>e.g.
  "This is a sentence"
  one part: "sentence"
  second part: "This is a " //Note there is whitespace at the end of this string</p>
  
  <p>"This is a "
  one part: ""
  second part: "This is a "</p>