title: How do I get the index of an object in an NSArray using string value?
body: <p>I want to get the index of an object within the NSMutableArray of categories. </p>
  
  <p>The category object has an attribute "category_title" and I want to be able to get the index by passing the value of category_title.  </p>
  
  <p>I have looked through the docs and can't find a simple way to go about this. </p>