Update UIImageView in a UITableView cell with transparency

I have an imageview class that subclasses the UIImageView class, it is being displayed in an UITableView that dequeueReusableCellWithIdentifier.

@interface ImageView : UIImageView {
.
.
.

when it is time to update the image from one image to another, the update itself works

[self setImage:[UIImage imageWithContentsOfFile:[self resourcesDir:url]]];

but my images are transparent PNG (with the same dimensions) so part of the pervious image is visible under the updated one (since the cells themselves are reused)

I tried various ways to make the imageView clear itself first, but none work, this is what I tried:

self.image = nil;

[self setBackgroundColor:开发者_JS百科[UIColor clearColor]]; 

[self setNeedsDisplay];

[self performSelectorOnMainThread:@selector(setNeedsDisplay) withObject:nil waitUntilDone:NO];

Any Idea ?

Be sure you are NOT using a new instance of the UIImageView. It must be the same instance for your code to work properly. You idea sounds like it should work properly.