ipad ios iphone判断 CGMutablePathRef是否为空

判断CGMutablePathRef是否存在

if (path != NULL)
  CGPathAddLineToPoint(path, NULL, point.x, point.y);

判断CGMutablePathRef是否含有元素

if (!CGPathIsEmpty(path))
  CGPathAddLineToPoint(path, NULL, point.x, point.y);