title: crash while removing objects from NSMutableArray
body: <p>In my iphone project (ARC enabled) i have a <code>nsmuatble</code> array which contains some 5 managed objects (which are retrieved from core data ) and in some scenario i need to remove all the objects from that <code>nsmutablearray</code></p>
  
  <p>i have used following methods to remove objects but its crashing in both the cases with the crash log <code>-[__NSArrayI removeObject:]: unrecognized selector sent to instance 0xa391640</code></p>
  
  <pre><code>if (surveys &amp;&amp; [surveys count]&gt;0)
          {
  
              [surveys removeAllObjects];
              surveys = [[NSMutableArray alloc]init];
          }
  </code></pre>
  
  <p>and also i tried</p>
  
  <pre><code>if (surveys &amp;&amp; [surveys count]&gt;0)
          {
              for(Survey *obj_Survey in surveys)
              {
                  [surveys removeObject:obj_Survey];
              }
  
              surveys = [[NSMutableArray alloc]init];
          }
  </code></pre>
  
  <p>can any one tell me how do i empty that array,, any suggestions would be appreciated, thanx in advance</p>