Objective c 对路径中的转换参数使用NULL和CGAffineTransformity的区别

以下各项之间是否存在任何差异，尤其是在性能方面：

方法1-使用空转换：

- (CGPathRef)createPathForRect:(CGRect)rect
{
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, NULL, rect.size.width / 2, rect.size.height - 1);
    CGPathAddLineToPoint(path, NULL, (rect.size.width / 2) - 20, rect.size.height - 22);
    CGPathAddLineToPoint(path, NULL, 0, rect.size.height - 22);
    CGPathAddLineToPoint(path, NULL, 0, 0);
    CGPathAddLineToPoint(path, NULL, rect.size.width - 1, 0);
    CGPathAddLineToPoint(path, NULL, rect.size.width - 1, rect.size.height - 22);
    CGPathAddLineToPoint(path, NULL, (rect.size.width / 2) + 20, rect.size.height - 22);
    CGPathCloseSubpath(path);
    return path;
}

- (CGPathRef)createPathForRect:(CGRect)rect
{
    CGAffineTransform transform = CGAffineTransformIdentity;
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, &transform, rect.size.width / 2, rect.size.height - 1);
    CGPathAddLineToPoint(path, &transform, (rect.size.width / 2) - 20, rect.size.height - 22);
    CGPathAddLineToPoint(path, &transform, 0, rect.size.height - 22);
    CGPathAddLineToPoint(path, &transform, 0, 0);
    CGPathAddLineToPoint(path, &transform, rect.size.width - 1, 0);
    CGPathAddLineToPoint(path, &transform, rect.size.width - 1, rect.size.height - 22);
    CGPathAddLineToPoint(path, &transform, (rect.size.width / 2) + 20, rect.size.height - 22);
    CGPathCloseSubpath(path);
    return path;
}

方法2-使用身份转换：

- (CGPathRef)createPathForRect:(CGRect)rect
{
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, NULL, rect.size.width / 2, rect.size.height - 1);
    CGPathAddLineToPoint(path, NULL, (rect.size.width / 2) - 20, rect.size.height - 22);
    CGPathAddLineToPoint(path, NULL, 0, rect.size.height - 22);
    CGPathAddLineToPoint(path, NULL, 0, 0);
    CGPathAddLineToPoint(path, NULL, rect.size.width - 1, 0);
    CGPathAddLineToPoint(path, NULL, rect.size.width - 1, rect.size.height - 22);
    CGPathAddLineToPoint(path, NULL, (rect.size.width / 2) + 20, rect.size.height - 22);
    CGPathCloseSubpath(path);
    return path;
}

- (CGPathRef)createPathForRect:(CGRect)rect
{
    CGAffineTransform transform = CGAffineTransformIdentity;
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, &transform, rect.size.width / 2, rect.size.height - 1);
    CGPathAddLineToPoint(path, &transform, (rect.size.width / 2) - 20, rect.size.height - 22);
    CGPathAddLineToPoint(path, &transform, 0, rect.size.height - 22);
    CGPathAddLineToPoint(path, &transform, 0, 0);
    CGPathAddLineToPoint(path, &transform, rect.size.width - 1, 0);
    CGPathAddLineToPoint(path, &transform, rect.size.width - 1, rect.size.height - 22);
    CGPathAddLineToPoint(path, &transform, (rect.size.width / 2) + 20, rect.size.height - 22);
    CGPathCloseSubpath(path);
    return path;
}

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我猜他们是完全一样的，但我想确认一下

如果查看文档中的函数，如

CGPathMoveToPoint

，它会这样说：

m
指向仿射变换矩阵的指针，如果不需要变换，则为NULL。如果指定，Quartz将在更改路径之前对点应用变换

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由于

CGAffineTransformity

本质上不是转换，因为它是标识，因此这两段代码实际上是相同的。

您测量过吗？仪器可能会给你一些想法。效果是一样的，但如果你只指定一个身份转换，石英似乎会做额外的工作。这就是我想确认的（我知道——这是一个微不足道的问题，但好奇心会杀死那只猫；）