Interface doesn't work

Hello,

I am creating a flash game. In this flash game the user has to estimate the weight of several products. I’ve created an interface for all ProductStacks to implement so i can take care of some stuff through calling the interface


package objects 
{    /**
     * ...
     * @author Mark
     */
    public interface IProductStack
    {
        function productScale():void;
        function get amount():Number;
        function get weight():Number;
    }
    
}

And this is a class implementing the methods:


package objects.stacks 
{
    import miracle.utils.NumberUtils;
    import objects.IProductStack;
    import objects.ProductStack;
    import flash.display.MovieClip;
    
    /**
     * ...
     * @author Mark
     */
    public class Bananas extends ProductStack implements IProductStack
    {
        public function get weight():Number
        {
            _weight = (!_weight) ? NumberUtils.ClamRandom(200, 300) : _weight;
            
            return _weight;
        }
        
        /* INTERFACE objects.IProductStack */
        
        public function productScale():void
        {
            
        }
        
    }
    
}

The get method ‘amount’ is implemented in the base class ProductStack. I used to have only ‘amount’ and ‘weight’ methods in my interface before, but when i added scaleProduct i recieved this error for all products (while i implemented scaleProduct on all Products):


method not implemented objects::IProductStack/objects:IProductStack::productScale()
   over-binding 0 in objects.stacks::Cucumbers
VerifyError: Error #1053: Illegal override of Cucumbers in objects.stacks.Cucumbers.
    at global$init()