尝试解决“超出范围”的编译错误：CodeBlocks，Linux Fedora

Question

Please help me understand the source of this error - I'm unable to tell if it's the code or the settings for the IDE. Although "out of scope" questions are very common I have searched the answers but nothing found that helps.

I'm following a C++ course online at SoloLearn. Further to their suggestion I've downloaded and set up Codeblocks in Linux so that I can follow the course by writing the code and compiling it inside the IDE rather than simply online via their browser window. Everything's been fine until now ;0/

So I'm following a lesson on "composition" and (again following their suggestions) have broken down their code and created separate files to define constructors/classes. However, despite believing I'm doing everything correctly, I keep getting this one "out of scope" error.

Here is their code, written on a single page. If I copy and paste into the IDE as a single file it compiles successfully, and my chosen terminal window pops up with the expected output:

#include <iostream>
using namespace std;

class Birthday {
public:
    Birthday(int m, int d, int y)
    : month(m), day(d), year(y)
    {  }
    void printDate()
    {
        cout<<month<<"/"<<day <<"/"<<year<<endl;
    }
private:
    int month;
    int day;
    int year;
};

class Person {
public:
    Person(string n, Birthday b)
    : name(n), bd(b)
    {  }
    void printInfo()
    {
        cout << name << endl;
        bd.printDate();
    }
private:
    string name;
    Birthday bd;
};

int main() {
Birthday bd(2, 21, 1985);
Person p("David", bd);
p.printInfo();
}

What I'm now doing is removing the first constructor definition into separate .h and .cpp files, like so:

#ifndef BIRTHDAY_H
#define BIRTHDAY_H


class Birthday
{
public:
    Birthday(int  m, int d, int y);
    void printDate();

private:
    int month;
    int day;
    int year;
};

#endif // BIRTHDAY_H

and

#include "Birthday.h"
using namespace std;

Birthday::Birthday(int m, int d, int y)
: month(m), day(d), year(y)
{ }

void printDate()
    {
        cout<<month<<"/"<<day <<"/"<<year<<endl;
    }

Whatever I do, I've cleaned, re-run the project files. I've deleted and recreated them. I've rebooted. But every time I try building, I get the following:

• error: cout was not declared in this scope
• error: month was not declared in this scope
• error: day was not declared in this scope
• error: year was not declared in this scope.

If the code had never worked at all I'd be looking harder at my tools, but why is it that copying it into separate files gives me this error?

Answer 1

You need to include iostream in either Birthday.cpp or Birthday.h. Second, the definition of printDate needs to be scoped to the class: Birthday::printdate .