IOS半透明贝塞尔曲线怎么绘制

以下是我的代码，但是没有效果

    - (void)drawRect:(CGRect)rect
 {
    for (MyBezierPath *path in self.allPathArray){
        [path strokeWithBlendMode:kCGBlendModeDifference alpha:0.1];
        [path.color set];
        [path stroke];
    }
}

https://bbs.csdn.net/topics/392203708