iOS: error: accessing unknown 'cornerRadius' component of a property

I'm getting the following exception which is driving me crazy:

error: accessing unknown 'cornerRadius' component of a开发者_如何转开发 property

This is the line of code:

    cell.imageView.layer.cornerRadius = 20.0;

I'm following this tutorial from December 2010: http://www.raywenderlich.com/2502/introduction-to-calayers-tutorial

According to the documentation UIImageView is a UIView. It has a CALAyer. CALayer has cornerRadius property. I'm on iOS 4.0.

thanks

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Use

#import <QuartzCore/QuartzCore.h>

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Have you correctly imported QuartzCore?

 #import <QuartzCore/QuartzCore.h>