title: Remove objects from NSArray
body: <p>I have a project with ARC.</p>
  
  <p>I have an <code>NSArray</code> whit some object inside. 
  At certain point I need to change the object in the array.</p>
  
  <p>Whit a <code>NSMutableArray</code> I'll do :</p>
  
  <pre><code>[array removeAllObjects];
  </code></pre>
  
  <p>and I'm sure that this method release all object contained in the array.
  But with an NSArray I can't do that! So, my question is: if I set array to <code>nil</code> and then re-initialize it, the old object contained in the array are really released from memory ? </p>
  
  <pre><code>array = nil;
  array = [[NSArray alloc] initWithArray:newArray];
  </code></pre>
  
  <p>Or I need to use <code>NSMutableArray</code> ?</p>