如何在 C++ 中将字符串转换为 char*？
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How do I convert a string to a char* in c++?
提问by Ptichka
I have an error in my program: "could not convert from string to char*". How do I perform this conversion?
我的程序中有一个错误：“无法从字符串转换为字符*”。如何执行此转换？
回答by Martin Broadhurst
If you can settle for a const char*, you just need to call the c_str()method on it:
如果你能满足于 a const char*，你只需要调用c_str()它的方法：
const char *mycharp = mystring.c_str();
If you really need a modifiable char*, you will need to make a copy of the string's buffer. A vectoris an ideal way of handling this for you:
如果您确实需要一个可修改的char*，则需要制作字符串缓冲区的副本。Avector是为您处理此问题的理想方式：
std::vector<char> v(mystring.length() + 1);
std::strcpy(&v[0], mystring.c_str());
char* pc = &v[0];回答by sbi
Invoke str.c_str()to get a const char*:
调用str.c_str()以获取const char*：
const char *pch = str.c_str();
Note that the resulting const char*is only valid until stris changed or destroyed.
请注意，结果const char*仅str在更改或销毁之前有效。
However, if you really need a non-const, you probably shouldn't use std::string, as it wasn't designed to allow changing its underlying data behind its back. That said, you can get a pointer to its data by invoking &str[0]or &*str.begin().
但是，如果您确实需要非const，则可能不应该使用std::string，因为它的设计不允许在背后更改其基础数据。也就是说，您可以通过调用&str[0]或来获取指向其数据的指针&*str.begin()。
The ugliness of this should be considered a feature. In C++98, std::stringisn't even required to store its data in a contiguous chunk of memory, so this might explode into your face. I think has changed, but I cannot even remember whether this was for C++03 or the upcoming next version of the standard, C++1x.
这种丑陋应该被认为是一个特征。在 C++98 中，std::string甚至不需要将其数据存储在连续的内存块中，因此这可能会引起您的注意。我认为已经改变，但我什至不记得这是针对 C++03 还是即将到来的下一版本标准 C++1x。
If you need to do this, consider using a std::vector<char>instead. You can access its data the same way: &v[0]or &*v.begin().
如果您需要这样做，请考虑使用 astd::vector<char>代替。您可以通过相同的方式访问其数据：&v[0]或&*v.begin()。
回答by Vatsan
//assume you have an std::string, str.
char* cstr = new char[str.length() +1];
strcpy(cstr, str.c_str());
//eventually, remember to delete cstr
delete[] cstr;
回答by John Dibling
Since you wanted to go from a stringto a char*(ie, not a const char*) you can do this BUT BEWARE: there be dragons here:
因为你想从 astring到 a char*（即，不是 a const char*）你可以这样做，但要注意：这里有龙：
string foo = "foo";
char* foo_c = &foo[0];
If you try to modify the contents of the string, you're well and truly on your own.
如果您尝试修改字符串的内容，那么您就完全靠自己了。
回答by aschepler
Use the c_str()method on a stringobject to get a const char*pointer. Warning: The returned pointer is no longer valid if the stringobject is modified or destroyed.
使用对象c_str()上的方法string来获取const char*指针。警告：如果string对象被修改或销毁，则返回的指针不再有效。
回答by Dialecticus
If const char*is good for you then use this: myString.c_str()
如果const char*对你有好处，那么使用这个：myString.c_str()
If you really need char*and know for sure that char*WILL NOT CHANGE then you can use this: const_cast<char*>(myString.c_str())
如果您确实需要char*并确定char*不会更改，那么您可以使用以下命令：const_cast<char*>(myString.c_str())
If char*may change then you need to copy the string into something else and use that instead. That something else may be std::vector, or new char[], it depends on your needs.
如果char*可能会更改，那么您需要将字符串复制到其他内容中并使用它。其他可能是std::vector，或者new char[]，这取决于您的需要。
回答by Bertrand Marron
std::string::c_str()returns a c-string with the same contents as the stringobject.
std::string::c_str()返回与string对象内容相同的 c 字符串。
std::string str("Hello");
const char* cstr = str.c_str();
