5.3.2 Header files and class

A class declaration would typically go into a header file say Example.h. The methods would typically get implemented in a separate file Example.cpp^5.3.

To illustrate this I have repackaged the struct-using example in 5.2.1 in:

class declaration
class method implementation
class use

(Note: these are in the file system also in /shared/teaching/CSLL/2061/Classes) In the header file the class Person is defined:

class Person {
 public:
  int age;
  int height;
  void print();
  void zero();
};

The methods are implemented in class method implementation, which has #include "Person.h" to access the class declaration:

#include <iostream>
#include "Person.h"
using namespace std;

void Person::zero() {
age = 0;
height = 0;
}

void Person::print() {
cout << " age " << age << '\n';
cout << " height " << height << '\n';
}

Note:

the function being implemented is prefaced by its class name. Member functions might have have input or return types, but in this case both are void
the print function of a Person object works on the age and height members of that object. Note the syntax carefully: the class members are treated syntactically like global variables. Syntactically they are neither input parameters of the function, nor local variables declared in the body.

The code using the class is user

#include <iostream>
#include "Person.h"
using namespace std;

int main() {
  Person fred;
  fred.age = 3;
  fred.height = 10;
  fred.print();
  fred.zero();
  fred.print();
}