如何在用户拖动时删除CAShapeLayer？

Question

我是绘画应用程序的新手，所以请建议我有什么方法可以删除。

我用谷歌搜索我只是

  CGContextSetBlendMode(_context, kCGBlendModeClear);

但不适用于CAShape图层

UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:CGPointMake(touchPoint.x,touchPoint.y)];
    [path addLineToPoint:CGPointMake(startingPoint.x,startingPoint.y)];

    CAShapeLayer *shapeLayer = [CAShapeLayer layer];

    shapeLayer.path = [path CGPath];
//    shapeLayer.strokeColor =kCGBlendModeClear;

    if([UIDevice currentDevice].userInterfaceIdiom ==UIUserInterfaceIdiomPad)
    {
        shapeLayer.lineWidth = 7.0;

    }
    else
    {
        shapeLayer.lineWidth = 5.0;

    }
    shapeLayer.fillColor = [[UIColor clearColor] CGColor];
    [self.layer addSublayer:shapeLayer];
    [clearBeizer addObject:shapeLayer];

请帮我删除该图层。