Handout 17

A Class Example

1. // Handout 17 - myClass.h
3. #ifndef MYCLASS_H
4. #define MYCLASS_H
6. class myClass {
7. public:
8.    myClass(int); // constructor
9.    ~myClass(); // destructor
10.    void addToMyClass(int);
11.    void subFromMyClass(int);
12.    void showValue();
13. private:
14.    int daValue;
15. };
17. #endif

1. // Handout 17 - myClass.cpp
3. // Implementation of the methods defined in myClass.h
5. #include <iostream>
6. #include "myClass.h"
7. using namespace std;
8. // constructor
9. myClass::myClass(int x) {
10.    daValue = x;
11.    cout << "myClass Constructor called" << endl;
12.    cout << "value of daValue is " << daValue << endl;
13. }
15. // destructor
16. myClass::~myClass() {
17.    cout << "myClass Destructor called" << endl;
18.    cout << "the value of daValue is " << daValue << endl;
19. }
21. void myClass::addToMyClass(int stuff_to_add) {
22.    daValue += stuff_to_add;
23. }
25. void myClass::subFromMyClass(int stuff_to_subtract) {
26.    myClass::addToMyClass(- stuff_to_subtract);
27. }
29. void myClass::showValue() {
30.    cout << "the value of daValue is " << daValue << endl;
31. }
33. // Handout 17 Class Example - myProgram.cpp
35. #include <iostream>
36. #include "myClass.h"
37. using namespace std;
38. int main() {
40.    myClass this_one(1); // create one instance
41.    myClass the_other_one(2); // create a second instance
43.    this_one.addToMyClass(3);
44.    this_one.subFromMyClass(2);
45.    this_one.showValue();
47.    the_other_one.addToMyClass(12);
48.    the_other_one.subFromMyClass(22);
49.    the_other_one.showValue();
51.    return 0;
52. }

output from the program is as follows:

myClass Constructor called
value of daValue is 1
myClass Constructor called
value of daValue is 2
the value of daValue is 2
the value of daValue is -8
myClass Destructor called
the value of daValue is -8
myClass Destructor called
the value of daValue is 2