title: cant able to exchanges elements in array
body: <p>hi i am new to iPhone.what i did is creating an array with images as shown below</p>
  
  <pre><code>images = [NSMutableArray alloc] initWithObjets:@"image1.jpg",@"image2.jpg",@"image3.jpg",@"image4.jpg",@"image5.jpg",@"image6.jpg",nil]
  </code></pre>
  
  <p>and i create a button when ever button click images are exchanged for that i am writing code as fallows in button clicked event.</p>
  
  <pre><code>[_images exchangeObjectAtIndex:2 withObjectAtIndex:4];
  </code></pre>
  
  <p>but images are not exchanged and i did n't get any warnings and images.i am writing array in viewDidLoad.what is the wrong.how can i exchange elements in the array. thank u in advance.</p>