Animate a property of a layer and implicitly animate the result.

[CoreAnimation]PropertiesAnimation.m

@dynamic theProperty; //The property should set as dynamic 

- (id)initWithLayer:(id)layer {
    
	if (self = [super initWithLayer:layer]) {

		if ([layer isKindOfClass:[PieMask class]]) {
            
			YourLayer *currentPresentation = (YourLayer *)layer;
			self.theProperty = currentPresentation.theProperty;
			//Add here any other properties needed for the animation 
			//I.E. self.anotherProperty = currentPresentation.anotherProperty;
    }
        
	}
	
	return self;
}

+ (BOOL)needsDisplayForKey:(NSString *)key {
	
    if ([key isEqualToString:@"theProperty"]) {
        
		return YES;
	}
	
	return [super needsDisplayForKey:key];
}

-(id<CAAction>)actionForKey:(NSString *)event {
    
	if ([event isEqualToString:@"theProperty"]{

        CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:event];
        anim.fromValue = [[self presentationLayer] valueForKey:event];
        anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
        anim.duration = 1.0;
            
        return anim;

	}
	
	return [super actionForKey:event];
}

- (void)drawInContext:(CGContextRef)ctx{
    
    // Draw the layer using theProperty...
}