I can't define a string in my C++ code in qt

Question

My code is as follows.

#include "test.h"
#include "string"
#include "iostream"
using namespace std::string::find;


test::test(){
    string str ("ffs test ffs");
    string str2 ("test");
    if (str.find(str2) != std::string::npos) {
        std::cout << "found" << "\n";
    } else {
        std::cout << "not found" << "\n";
    }
}

the issue I'm having is this, when trying to define a string in the C++ file qt states "unknown type name 'string'". Also on line 4 my 'import' highlights string as if it doesn't exist, despite it being an option the editor suggests to me while I'm typing it. What am I doing wrong here? Everything I find is to try and fix issues passing stuff to QStrings and nothing related to my issue as far as I can tell. I've tried both types of importing #include <thing> and #include "thing" on all the imports it doesn't seem to make a difference.

This has nothing to do with Qt. Have you tried proper includes like `#include `? — Matthieu Brucher, Oct 25 '18 at 11:07
yes, ive tried it both ways round exact same error is stated — problemlow, Oct 25 '18 at 11:08

score 4 · Accepted Answer · answered Oct 25 '18 at 11:11

4

Use std::string instead of string.

#include "test.h"
#include <string>
#include <iostream>

test::test(){
    std::string str ("ffs test ffs");
    std::string str2 ("test");
    if (str.find(str2) != std::string::npos) {
        std::cout << "found" << "\n";
    } else {
        str::cout << "not found" << "\n";
    }
}

Don't use using namespace (of course in your case, it wasn't a namespace, so that's another error), use <> for system headers.

answered Oct 25 '18 at 11:11

Matthieu Brucher

21,634
7
38
62

This is an interesting answer. Could you explay *why* one shouldn't use `using namespace`? – TimSch Oct 25 '18 at 12:08
https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice – Matthieu Brucher Oct 25 '18 at 12:09

score 2 · Answer 2 · answered Oct 25 '18 at 11:17

After inclusion of the appropriate headers iostream, string etc, you can write:

using std::string;

This will bring in only string from the namespace std into your program. And you can do this if you want to avoid typing std::string everywhere. You can do this for stream objects like cout, cin as well.

using std::cout;
using std::cin;

score 1 · Answer 3 · answered Oct 25 '18 at 13:05

1

Use Scope operator :: in Your Code and Access manually to std class

std::string

it will help you !

answered Oct 25 '18 at 13:05

Mohammad Mahdi Mohajer

601
5
9

I can't define a string in my C++ code in qt

3 Answers3