Error: "x" was not declared on this scope when using class files

Question

I'm having a problem when using the class files and the compiler error says "error: 'x' was not declared on this code" while it points out the cout, string, and endl. I have already wrote "#include " and "#include " in both header, class, and main file.

(Sorry for my English) I'm just a beginner and I wanted to know the basics

Added #include and #include in both files

//Main File (main.cpp)
#include <iostream>
#include "test.h"
#include <string>
using namespace std;

int main()
{
    test *person = new person("Phroton",14)
    person.Display();
    return 0;
}

//test.h
#ifndef TEST_H
#define TEST_H
#include <iostream>
#include <string>
class test
{
    private:
        string name;
        int age;
    public:
        void Display(){
            cout << "I'm " << name << " and I'm " << age << "years old" << endl;
        }
};

#endif // TEST_H

//test.cpp (There is no problem with this file at all)
#include "test.h"
#include <iostream>
#include <string>
test::test(string iname, int iage)
{
    name = new string;
    age = new int;
    *name = iname;
    *age = iage;
}

test::~test()
{
    delete name;
    delete age;
    cout << "Info Deleted" << endl;
}

You appear to be misusing new 100% of the time in this code. I'd recommend unlearning new until you get familiar enough with C++ that it's time to move from self-contained learning code to real-world legacy code. — chris
Hi and welcome to SO. Do you want to stick to the pointers?? — skratchi.at
To learn the basics, get a good book and start with chapter one. Read the text (don't just look at the code), do the exercises, don't skip ahead. Stay away from online tutorials. — molbdnilo

P.W P.W · Accepted Answer · 2019-05-08T05:08:54

Answering the specific problem you have asked:

This is because you have not specified the namespace cout and endl belong to in the file test.h.

The statement in Display should be:

std::cout << "I'm " << name << " and I'm " << age << "years old" << std::endl;

The alternative to this is the using namespace std declaration but this is considered a bad practice (especially in a header file).

Note:

You do not need using namespace std in main.cpp as you are not using any functions from the std namespace there. Even if you do, use the std::name instead of the using declaration.
Member function definitions are usually present in .cpp files. So you can define the function Display to test.cpp.
Also consider moving away from raw pointers to smart pointers.

Error: "x" was not declared on this scope when using class files

1 Answers