Undefined variables within header files - c++

Question

Thanks for taking the time to view my question. I've spent a lot of time looking but can't find a solution to this problem:
I have a class Person with its' respective Header file Person.h. The cpp class is having a hard time understanding what the variables name, age, and iq are.
//Person.cpp
/*
Makes a person.
A person has a name, an age, and an IQ level.
We will create many of these objects within other classes.
*/
#include "Person.h"
Person::Person() //Empty constructor
{
}
Person::Person(string thename, int theage, int theiq)
{
name = thename;
age = theage;
iq = theiq;
}
string getName()
{
return name; //Error: identifier "name" is undefined
}
int getAge()
{
return age; //Error: identifier "age" is undefined
}
int getIq()
{
return iq; //Error: identifier "iq" is undefined
}
void setName(string aName)
{
name = aName; //Error: identifier "name" is undefined
}
void setAge(int aAge)
{
age = aAge; //Error: identifier "age" is undefined
}
void setIq(int aIq)
{
iq = aIq; //Error: identifier "iq" is undefined
}
The Header File
//=================================
// include guard
#ifndef __PERSON_H_INCLUDED__
#define __PERSON_H_INCLUDED__
//=================================
// forward declared dependencies
//=================================
// included dependencies
#include <string> //For the name
//=================================
using namespace std;
class Person
{
public:
Person(); //Default constructor
Person(string thename, int theage, int theiq); //Constructor
string getName();
int getAge();
int getIq();
void setName(int aName);
void setAge(int aAge);
void setIq(int aIq);
private:
string name;
int age, iq;
};
#endif //__PERSON_H_
SURELY I don't have to define the variables inside Person.cpp right? It already knows exactly what variables name, age, and iq are because it saw the header file already. Why can it not understand what those variables are?
If I do, or if there is anything I'm missing, make sure to really spell it out for me. I'm barely an intermediate C++ programmer so I may not understand jargon. Even things like scope, inheritance, and definitions go way over my head.
Thank you for your time.

Answer 1

To which ever part you're getting errors do this:
return type Person::function name(parameters)
For the declaration part of the functions.
For example for the getAge function do this:
int Person::getAge() {
return age;
}
The reason you got errors is because of the following:
First your intention was to define the functions you declared in the Person class.
In the return statement you wanted to return age member of the Person class. But you simply returned age.
The search for age begins inside the function body first. If its not found it is searched in the outer scope. If its still not found age is an unknown identifier.
After you fix it what happens is this:
The Person:: part in the return type Person::function name(parameters) means that look in the scope of the Person class.
Then in the return statement we return age member of the Person class. But this time we're looking inside the scope of the Person class, hence we return the age member and the error is fixed.

Answer 2

You need to change
string getName()
to
string Person::getName()
in the .cpp file. Ditto for the others., The compiler needs to know that this is a part of the class Person.

Answer 3

Your function
string getName()
{
return name; //Error: identifier "name" is undefined
}
is not defining the class member function. Instead you are declaring and defining a (completely different and unrelated) free function. As such, name is undefined within the scope of this function.