gistfile1.m

CGPoint _firstLocation;
CGFloat _startY, _yMinValue = 74.0f, _yFullSize, _yExtraSpace;

- (void)panRecognizerAction:(UIPanGestureRecognizer *)recognizer
{
  CGPoint location = [recognizer locationInView:self];
         
	if (recognizer.state == UIGestureRecognizerStateBegan)
    {
		_startY = self.frame.size.height;
		_firstLocation = location;
        _yFullSize = 130;
        _yExtraSpace = 100.0f;
	}
	
	CGFloat newHeight = _startY - (_firstLocation.y - location.y);
    
    if (newHeight < _yMinValue) newHeight = _yMinValue;
    
	BOOL overlimit = newHeight > _yFullSize;
    
	if (overlimit)
    {
		//width of the area the finger can pan after the menu width
		CGFloat overlimitWidth = _yFullSize + _yExtraSpace;
        
		//we take the position of the finger in this area as a percentage
		CGFloat overlimitProgress = 1-((overlimitWidth-newHeight)/_yExtraSpace);
        
        CGFloat easeOutFactor = atan(overlimitProgress);
        
        newHeight = _yFullSize + (_yExtraSpace*easeOutFactor);

	}
    
    if (recognizer.state != UIGestureRecognizerStateEnded &&
        recognizer.state != UIGestureRecognizerStateFailed &&
        recognizer.state != UIGestureRecognizerStateCancelled)
    {
        self.frame = CGRectMake(0, 0, self.frame.size.width, newHeight);
    }
	
	if (recognizer.state == UIGestureRecognizerStateEnded)
    {
        CGPoint velocity = [recognizer velocityInView:self];
        
		if (newHeight > 170)
        {
            [self openToFull:velocity.y];
		}
        else
        {
			if (velocity.y < 0)
            {
                [self openToMin:velocity.y];
            }
            else
            {
                [self openToFull:velocity.y];
            }
		}
	}
}