NSString 弱持有 std::string 的 const char *
NSString 弱包含属于 std::string 的 const char * 最安全的方法是什么？下面的两个示例都适用于日志中的简单测试，并如 NSTableView 中所示，但我担心实际的奇怪行为。可能是 c_str() 的额外空字符被简单地忽略（因为传递了长度参数），并且任何一个都可以正常工作。
鉴于：
std::string const * stdstring = new std::string("Let's see if this works");
那么：
NSString * aStr = [[NSString alloc] initWithBytesNoCopy:
stdstring->data() length: stdstring->length()
encoding:NSUTF8StringEncoding freeWhenDone:NO];
或：
NSString * aStr2 = [[NSString alloc] initWithBytesNoCopy:
stdstring->c_str() length: stdstring->length()
encoding:NSUTF8StringEncoding freeWhenDone:NO];
或者其他什么？
What's the safest way for a NSString to weakly contain a const char * belonging to a std::string? Both examples below work on a simple test, in logs, and as presented in a NSTableView, but I'm concerned about strange behavior down to road. It may be the extra null character of c_str() is simply ignored (because of the length parameter passed) and either will work fine.
Given:
std::string const * stdstring = new std::string("Let's see if this works");
Then:
NSString * aStr = [[NSString alloc] initWithBytesNoCopy:
stdstring->data() length: stdstring->length()
encoding:NSUTF8StringEncoding freeWhenDone:NO];
or:
NSString * aStr2 = [[NSString alloc] initWithBytesNoCopy:
stdstring->c_str() length: stdstring->length()
encoding:NSUTF8StringEncoding freeWhenDone:NO];
or something else?
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initWithBytesNoCopy:length:...的文档明确指出length将是使用的字节数，因此空终止字符将始终被忽略。因此，data()和c_str()返回的内存内容同样合适。考虑到这一点：
std::string的data()和c_str()函数返回的内存的生命周期保证是相同的- 它们将一直存在，直到您在字符串对象上调用非常量成员函数。这取决于内部数据结构是否已经是空终止字符数组的实现，因此一般来说，data()会比c_str()更便宜或复杂度相同>。因此我会选择data()。The documentation for
initWithBytesNoCopy:length:...clearly states that thelengthwill be the number of bytes used, so the null termination character will always be ignored. Hence the contents of the memory returned bydata()andc_str()is equally suitable.With that in mind:
The lifetime guarantees of the memory returned by
std::string'sdata()andc_str()functions are identical - they will survive until you call a non-const member function on the string object. It depends on the implementation whether the internal data structure is already a null-terminated character array, so in general,data()will be cheaper or identical in complexity toc_str(). I'd therefore go fordata().