remove memory of CATransition
<p>I used the codes below to display a image via CATransition  </p>

<pre><code>NSString *s0 = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"black.png"];//black.png is square image with black color back ground


NSData *imageData0 = [NSData dataWithContentsOfFile:s0];
UIImage *image0 =[UIImage imageWithData:imageData0];
[fromUIView setImage:image0];
[fromUIView setHidden:false];

CATransition *transition = [CATransition animation];
transition.duration = duration; 
transition.timingFunction = [CAMediaTimingFunction  functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
transition.delegate = self;
transition.type = types[type];
transition.subtype = subtypes[subType];
[self.View1.layer addAnimation:transition forKey:nil];
fromUIView.hidden = YES; 
toUIView.hidden = NO;
UIImageView *tmp = toUIView;//toUIView is UIImageView and is what I hope to display
toUIView = fromUIView;
toUIView = tmp;
</code></pre>

<p>It works well at the first time, but if I call the codes again, it always display toUIView image at the last time, then do transition</p>

<p>I try to use</p>

<pre><code>fromUIView.image=nil;
</code></pre>

<p>to remove/clear the toUIView, but it still display image of toUIView </p>

<p>Welcome any comment</p>
