Converting string to const* char

Question

I have two string declarations:

killerName
victimName

I need to convert these two string values to const* char.

Example of how I use my method:

if (killer.IsRealPlayer) {
   killerName = killer.GetName(); -- need to convert to const* char
   victimName = victim.GetName(); -- need to convert to const* char

   Notice(killerName + "has slain:" + victimName, killer.GetMapIndex(), false); 
}

Some error I receive:

Error 111 error C2664: 'Notice' : cannot convert parameter 1 from 'std::basic_string<_Elem,_Traits,_Ax>' to 'const char */

This is really unclear. The output and code do not match your question or title. — Lightness Races in Orbit, Apr 03 '14 at 22:58
http://stackoverflow.com/questions/8126498/how-to-convert-a-const-char-to-stdstring — Engineer2021, Apr 03 '14 at 22:59
And your new edit is completely off-target. Do you know what happens if you do `const char*` + `"has slain:"` + `const char*` ? — Ben Voigt, Apr 03 '14 at 23:04
How about downloading the the [standard](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3337.pdf)? — Deduplicator, Apr 03 '14 at 23:04
Possible duplicate of [How to convert a std::string to const char\* or char\*?](http://stackoverflow.com/questions/347949/how-to-convert-a-stdstring-to-const-char-or-char) — Andrii Abramov, Oct 05 '16 at 11:06

score 4 · Accepted Answer · answered Apr 03 '14 at 23:04

It seems that function Notice have the first parameter of type const char * However the expression passed to it as the first argument

killerName + "has slain:" + victimName

has type std::string

Simply call the function the following way

Notice( ( killerName + "has slain:" + victimName ).c_str(), killer.GetMapIndex(), false);

Suedocode · Answer 2 · 2014-04-03T23:04:15.977

3

Notice(string(killerName + "has slain:" + victimName).c_str(), killer.GetMapIndex(), false);

std::string::c_str() gives the const char* to the buffer. I think that's what you want.

See: http://www.cplusplus.com/reference/string/string/c_str/

edited Apr 03 '14 at 23:04

answered Apr 03 '14 at 22:58

Suedocode

2,504
3
23
41

score 1 · Answer 3 · answered Apr 03 '14 at 23:30

As others already wrote, the result of killerName + "has slain:" + victimName is of type std::string. So, if your Notice() function expects a const char* as first parameter, you must convert from std::string to const char*, and since there is no implicit conversion defined for std::string, you must call the std::string::c_str() method:

Notice((killerName + "has slain:" + victimName).c_str(), killer.GetMapIndex(), false);

However, I'd like to ask: why do you have Notice() expecting a const char* as first parameter?
Would it be better to just use const std::string&? In general, in modern C++ code, you may want to use string classes like std::string instead of raw char* pointers.

(Another option would be to have two overloads of Notice(): one expecting a const std::string& as first parameter, and the other one expecting a const char*, if for some reason the const char* version does make sense in your particular context; this double overload pattern is used e.g. in the std::fstream constructor.)

Converting string to const* char

3 Answers3