Right usage of destructor

Question

I just started working with C++ and now I have a really basic question.

I wrote 2 classes:

Coordinate:

#include <stdio.h>

class Coordinate {
private:
    int x;
    int y;
public:
    Coordinate(int a, int b) {
        x = a;
        y = b;
    };
    void printTest() {
        printf("%d %d\n", x, y);
    };
};

Test:

class Test {
private:
    int q;
    Coordinate *point;
public:
    Test(int a, int b, int c) {
        q = a;
        point = new Coordinate(b, c);
    };
    virtual ~Test() {
        delete point;
    }
};

main function:

int main() {
    Test *test = new Test(1, 2, 3);
    // ...
    delete test;
    return 0;
}

In my main I worked with an object of the Test class. I wrote my own Test destructor but I am not sure if this destructor work like expected. Does it completly deallocte the memory from test? Or do I have to do something with the q attribute to deallocate it?

Answer 1

Yes, this is the correct usage of a C++ destructor (your destructor in Test does not need the virtual keyword as there is no inheritance in your example).

As a rule of thumb every new should be followed by a delete, but when you're using class and instantiation it becomes more subtle than that. Following the Rule of Three or Five, when a class uses dynamic memory you should redefine the class destructor to deallocate accordingly, which you did, so great!

In your program execution, when delete test is invoked it will first deallocate the dynamic memory of point, before deallocating the dynamic memory you set in your main function with your test attribute. In this way you're not leaking memory (yay!) and your memory management has been done accordingly :)