title: Ruby .reject! vs .delete_if
body: <p>Being new to Ruby, I have a question about the difference between the .reject! and .delete_if methods when dealing with hashes and arrays. If just wanting to get rid of certain objects, is there functionally any difference between the methods? And reason to use one over the other?</p>
  
  <p>Thanks!</p>
  
  <p><strong>EDIT</strong>
  I have read the documentation...I guess I should have been more clear in my original question. I was wondering more about differences in efficiency. Do they operate differently in how they delete items? (Again, ignoring return value. I understand that is a difference. Thanks!)</p>