title: Creating an array from properties of objects in another array
body: <p>Is there any convenient way to take an array/set of objects and create a new array/set containing some property of each item in the first array?</p>
  
  <p>For example, an array contains Car objects.  I need an array of licensePlates, where each car has an NSObject car.licensePlate.</p>
  
  <p>Currently I just iterate through the first array adding objects to my mutable results array, but was wondering if there is an instantiation method that exists for this (checked the docs for NSArray).</p>