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Convert std::string to const char* or char*

2014-03-07 18:37 633 查看

Q:

How can I convert an

std::string

to
a

char*

or
a

const
char*

?

A:

If you just want to pass a

std::string

to
a function that needs

const
char*

you can use

std::string str;
const char * c = str.c_str();

If you want to get a writable copy, like

char
*

, you can do that with this:

std::string str;
char * writable = new char[str.size() + 1];
std::copy(str.begin(), str.end(), writable);
writable[str.size()] = '\0'; // don't forget the terminating 0

// don't forget to free the string after finished using it
delete[] writable;

Edit: Notice that the above is not exception safe. If anything between the new call and the delete call throws, you will leak memory, as nothing
will call delete for you automatically. There are two immediate ways to solve this.

boost::scoped_array

boost::scoped_array

will
delete the memory for you upon going out of scope:

std::string str;
boost::scoped_array<char> writable(new char[str.size() + 1]);
std::copy(str.begin(), str.end(), writable.get());
writable[str.size()] = '\0'; // don't forget the terminating 0

// get the char* using writable.get()

// memory is automatically freed if the smart pointer goes
// out of scope

std::vector

This is the standard way (does not require any external library). You use

std::vector

,
which completely manages the memory for you.

std::string str;
std::vector<char> writable(str.size() + 1);
std::copy(str.begin(), str.end(), writable.begin());

// get the char* using &writable[0] or &*writable.begin()

From:http://stackoverflow.com/questions/347949/convert-stdstring-to-const-char-or-char

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