How to do it...

1. Go to Xcode and create a new playground file called Closures to test code about closures in it.
2. To see closures in action, copy and paste this piece of code in the playground file (the output of each statement is printed on the right):

      var names = ["David", "Jones", "Suzan", "Naomi", "Adam"] 
 
      names.sort() // ["Adam", "David", "Jones", "Naomi", "Suzan"] 
      names.sort{ (str1: String, str2: String) ->Bool in 
        return str1 > str2 
      } 
 
      // ["Suzan", "Naomi", "Jones", "David", "Adam"]