How to empty an std::string?

Question

This part of my code runs in an infinite loop and shows a number, but I need to empty the string after the use because, since it run in a loop, its keep being multiplied. (Sorry for my english, it's not my native language)

text ---> text text ----> text text text

cartemap << "Carte: " << currentmap;  //cartemap is a std:string currentmap a integer'

MESSAGE1 = TTF_RenderText_Solid( font,  cartemap.str().c_str() , noir );

apply_surface( 70, 70, MESSAGE1, SCREEN );

SDL_FreeSurface(MESSAGE1);

`cartemap` is not a `std::string`. `std::string` has no member function named `str`. It appears to be a `std::ostringstream`. — Benjamin Lindley, Dec 21 '13 at 04:10
`//cartemap is a std:string` --> [Comments are lies](http://johnsy.com/blog/entry/20121031130012)! Perhaps show the declaration next time. — johnsyweb, Dec 21 '13 at 04:29

johnsyweb · Answer 1 · 2013-12-21T23:57:00.180

5

Answering the question in the title

Call std::string::clear() to clear a string:

mystring.clear();

Answering the code in the post

But it looks like you need std::ostringstream::str() to clear an ostringstream (or stringstream) in your example:

cartemap.str("");

edited Dec 21 '13 at 23:57

answered Dec 21 '13 at 04:04

johnsyweb

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It doesnt work it keep being added – user3105169 Dec 21 '13 at 04:08
@user3105169: It seems you wish to clear an `ostringstream`, not a `string`. I've updated my answer to accommodate both. – johnsyweb Dec 21 '13 at 04:13
It worked (second option) – user3105169 Dec 21 '13 at 04:21

score 1 · Answer 2 · answered Dec 21 '13 at 04:04

1

If cartemap is your string, try this:

cartemap.resize(0);

http://www.cplusplus.com/reference/string/string/resize/

answered Dec 21 '13 at 04:04

benathon

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It gave me this : 'struct std::stringstream' has no member named 'resize'| – user3105169 Dec 21 '13 at 04:11

score 1 · Answer 3 · answered Dec 21 '13 at 04:12

1

AFAICT from your snippet, cartemap is not an std::string, but it's std::stringstream or similar. To empty a string stream, do

cartemap.str("");

answered Dec 21 '13 at 04:12

Matteo Italia

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You – user3105169 Dec 21 '13 at 04:14

How to empty an std::string?

3 Answers3

Answering the question in the title

Answering the code in the post