string 、char*、const char *

string 、char*、const char *  

1.string to char*
方式1
std::string str = "string";
char* chr = const_cast<char*>(str.c_str())

方式2
string str = "some string" ;
char *cstr = &str[0];

方式3
std::string str = "string";
const char *cstr = str.c_str();

Note that it returns a const char *; you aren’t allowed to change the C-style string returned by c_str(). If you want to process it you’ll have to copy it first:
std::string str = "string";
char *cstr = new char[str.length() + 1];
strcpy(cstr, str.c_str());
// do stuff
delete [] cstr;

Or in modern C++:
std::vector<char> cstr(str.c_str(), str.c_str() + str.size() + 1);
// use &chars[0] as a char*

2. char* to string
方式1：直接赋值：
char c[] = "this is a char array";
const char* t = "const char";
string s = t;
string ss = c;

同理const char*转string：
const char* cc = "this is a const exp";
string s(cc, cc + strlen(cc));

3. char* 和const char*
const char* src = "this is a const exp";
char* ch = const_cast<char*>(src);
const char* dst = static_cast<const char*>(ch);
cout << ch << endl;
cout << dst << endl;