C++ string in classes

Question

I know this is quite a ridiculous question but this is quite confusing and irritating, as something that should work simply is not. I'm using Code Blocks with the GCC compiler and I am trying to simply create a string variable in my class

#ifndef ALIEN_LANGUAGE
#define ALIEN_LANGUAGE

#include <string>

class Language
{
    public:

    private:
        string str;
};

#endif

Strange enough, my compiler halts me with an error saying this:

C:\Documents and Settings\...|11|error: `string' does not name a type|
||=== Build finished: 1 errors, 0 warnings ===|

For some reason, it is unable to find the class "string" which for some reason, my main.cpp is able to detect "#include " while my language class is not able for some reason.

This is the main I wrote quickly just to see it main itself is able to see the string file:

//main.cpp

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

using namespace std;

int main()
{
    string str;

    return 0;
}

Does anyone know what's going on?

Solution 1

using namespace std;

That's what's going on.

You don't have std:: prefixing the string in your class. Everything in the standard library is in the namespace std.

It is generally regarded as bad practice to use using namespace std;, by the way. For more information on why and what to do instead, check out this question: Using std Namespace.

Solution 2

The string class is defined in the std namespace. You should chenge the class to this:

class Language
{
    public:

    private:
        std::string str;
};

It is also possible, but not recommended to add this to the top of the header file:

using namespace std;

Solution 3

string is in namespace std, and you need to qualify it fully inside your header file:

#include <string>

class Language
{
    public:

    private:
        std::string str;
};

Do not use using namespace std; or similar in header files.

Solution 4

You should refer to it as std::string;

Solution 5

It looks to me like you're missing the all-important (with a hint of sarcasm) using namespace std; line. Either add that in before your class, or explicitely use std::string str. I'd recommend against adding the using namespace std; line in a header file, as it would pollute the mainspace for any file that includes it.

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Comments

[Admin]

Thank you, I've completely forgot that string the std:: prefixing, I'm used to not putting using namespace std; in my class files, but doing so in my main.cpp

[sbi]

Ah, someone not recommending using namespace std;! +1

[Mogi]

why not to using namespace std; in header files?

[Mogi]

nevermind, find the appropriate answer after googling: cplusplus.com/forum/beginner/25538 leaving these comments for future confusions