title: How to check if a NSMutableArray contains a value (null) or not?
body: <p>I have an <code>NSMutableArray</code> instance which contains "N" number of objects and I want to check whether <code>NSMutableArray</code> contains a (null) or any other value.</p>
  
  <p>In <code>NSString</code> there is a method called <code>isEqualToString:</code> Is there a similar method available for <code>NSMutableArray</code>?</p>
  
  <p>Or otherwise, how can I do this?</p>