C++ 如何将 std::string 转换为 const char*？
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How to convert std::string to const char*?
提问by Richard Knop
Possible Duplicate:
Convert std::string to const char* or char*
void Foo::bar(const std::string& foobar) {
// ...
const char* foobar2 = (char*)foobar;
// ...
}
That does not work and I get an error during compilation about invalid casting.
这不起作用，我在编译期间收到有关无效转换的错误。
Is there some other way to convert std::stringto const char*?
有没有其他方法可以转换std::string为const char*？
回答by
Use foobar.c_str().
使用 foobar.c_str().
You might find this link useful: http://www.cppreference.com/wiki/string/start
您可能会发现此链接很有用：http: //www.cppreference.com/wiki/string/start
回答by wkl
std::string::c_str()gets you a const char*pointer to a character array that represents the string (null-terminated).
std::string::c_str()为您提供一个const char*指向表示字符串（以空字符结尾）的字符数组的指针。
You should not manipulate the data this pointer points to, so if you need to do that, copy the data.
您不应该操作此指针指向的数据，因此如果您需要这样做，请复制数据。
Double edit - doing it in a more C++ fashion
双重编辑 - 以更 C++ 的方式进行
Since it is nicer to avoid the use of raw pointers and arrays where possible, you can also get the data into an std::vector<char>
由于在可能的情况下避免使用原始指针和数组更好，因此您还可以将数据放入 std::vector<char>
#include <string>
#include <vector>
int main()
{
std::string str = "Hello";
std::vector<char> cvec(str.begin(), str.end());
// do stuff
}
edit this is more like C since it uses raw pointers and explicitly allocates mem
编辑这更像 C，因为它使用原始指针并显式分配内存
#include <string>
#include <cstring>
int main()
{
std::string str = "Hello";
char *cptr = new char[str.size()+1]; // +1 to account for class Something {
const char* name;
public:
Something(const std::string& pname) {
this->name = pname.c_str(); /* wrong! the pointer will go wrong as the object from the parameter ceases to exist */
}
};
byte
std::strncpy(cptr, str.c_str(), str.size());
// do stuff...
delete [] cptr;
}
回答by Kos
You're going to get a lot of kinda incorrectanswers about str.c_str()here. :) While c_str()is indeed useful, please keep in mind that this will not actually convert the string into a char*, but rather return the contents of the string as a const char*. And this is a big difference!
你会在这里得到很多有点不正确的答案str.c_str()。:) 虽然c_str()确实很有用，但请记住，这实际上不会将字符串转换为 achar*，而是将字符串的内容作为 a 返回const char*。这是一个很大的不同！
What's important here is that the pointer you obtain from c_str()is valid only as long as the given stringobject exists. So this would be terribly wrong:
这里重要的是，您从中获取的指针c_str()仅在给定string对象存在时才有效。所以这将是非常错误的：
char* convert(const std::string& str) {
char* result = new char[str.length()+1];
strcpy(result,str.c_str());
return result;
}
So if you want to convert, as in: create a new value which will be independent of the original std::string, then you'll want to do something like this:
因此，如果您想进行转换，例如：创建一个独立于原始值的新值std::string，那么您将需要执行以下操作：
const char* foobar2 = foobar.c_str();
But still c_str()will be quite enough for you in most cases. Just try to think in terms of objects' time of life.
但c_str()在大多数情况下对你来说仍然足够了。试着从对象的生命周期来思考。
回答by fabrizioM
Notice the const. Otherwise you have to copy it to a char buffer.
注意const。否则，您必须将其复制到字符缓冲区。
