title: Adding blink animation in iOS without using NSTimer
body: <p>I want to add a blink animation in my app. For that purpose, I have used the code below.  </p>
  
  <pre><code>if (buttonFlashing) return;
          buttonFlashing = YES;
          self.img_one.alpha = 1.0f;
          [UIView animateWithDuration:0.12
                                delay:0.0
                              options:UIViewAnimationOptionCurveEaseInOut |
           UIViewAnimationOptionRepeat |
           UIViewAnimationOptionAutoreverse |
           UIViewAnimationOptionAllowUserInteraction
                           animations:^{
                               self.img_one.alpha = 0.0f;
                           }
                           completion:^(BOOL finished){
                               // Do nothing
                           }];
          mode_count=1;
  </code></pre>
  
  <p>It works fine to hide &amp; show the image view but I want to show another image when image is hidden then again show the previous image using above code. Above code just hides &amp; shows the image view by using it's alpha. How can I do it?</p>