在iPad 1上崩溃但不是> iPad 1

Question

考虑以下代码：

CGFloat largerLineSpacing = kStreamCellParagraphSpacing;

CTParagraphStyleSetting paragraphSettings[1] = {
    { kCTParagraphStyleSpecifierParagraphSpacing, sizeof(CGFloat), &largerLineSpacing }
};
CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphSettings, sizeof(*paragraphSettings));

在iPad 1（5.1）上运行时，此代码与EXC_BAD_ACCESS崩溃，但不是5.1模拟器或iPad 3（6.0）。 我的C很弱 - 我是否因为sizeof而犯了一个愚蠢的错误？

Answer 1

CTParagraphStyleCreate的文档表明它的第二个参数给出了paragraphSettings数组中的CTParagraphStyleSetting实例的数量（在你的例子中为1），而不是数组的字节大小。

如果您将代码更改为

CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphSettings, 1);

它应该工作。 或者，如果您想要应对将来添加更多设置，您可以尝试

int numElems = sizeof(paragraphSettings)/sizeof(paragraphSettings[0]);
CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphSettings,
                                                            numElems);

Answer 2

static CFIndex const settingCount = 1;

CTParagraphStyleSetting paragraphSettings[settingCount] = {
    { kCTParagraphStyleSpecifierParagraphSpacing, sizeof(CGFloat), &largerLineSpacing }
};

CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphSettings, settingCount);