通过指针枚举NSString字符

Question

如何通过拉出每个unichar来枚举NSString？我可以使用characterAtIndex,但这比通过递增的unichar*更慢.我没有在Apple的文档中看到任何不需要将字符串复制到第二个缓冲区的内容.

这样的事情是理想的:

for (unichar c in string) { ... }

要么

unichar* ptr = (unichar*)string;

Answer 1

您可以-characterAtIndex:通过首先将其转换为IMP表单来加快速度:

NSString *str = @"This is a test";

NSUInteger len = [str length]; // only calling [str length] once speeds up the process as well
SEL sel = @selector(characterAtIndex:);

// using typeof to save my fingers from typing more
unichar (*charAtIdx)(id, SEL, NSUInteger) = (typeof(charAtIdx)) [str methodForSelector:sel];

for (int i = 0; i < len; i++) {
    unichar c = charAtIdx(str, sel, i);
    // do something with C
    NSLog(@"%C", c);
}  

编辑:似乎CFString参考包含以下方法:

const UniChar *CFStringGetCharactersPtr(CFStringRef theString);

这意味着您可以执行以下操作:

const unichar *chars = CFStringGetCharactersPtr((__bridge CFStringRef) theString);

while (*chars)
{
    // do something with *chars
    chars++;
}

如果您不想分配内存来处理缓冲区,那就可以了.