destructor in C++

Destructor is a member function invoked automatically when an object is destroyed. It is the last function called when an object is destroyed. The destructor is called before member variables are destroyed.
If the object is created by using new, the destructor should use delete to free the memory.   
Properties of Destructor:
* There is only one destructor in a class with class name preceded by a tilde(~), no parameters and no return type.
* A destructor should be declared in the public section of the class.
* It cannot be declared static or const/volatile.
* It has no return type not even void.
* It is always a good idea to make destructors virtual in base class when we have a virtual function.
* An object of a class with a destructor cannot become a member of a union.
* The programmer cannot access the address of destructor.

A destructor function is called automatically when the object goes out of scope: 
* the function ends 
* the program ends 
* a block containing local variables ends 
* a delete operator is called

```
#include <string.h>
#include <iostream>

class String {
private:
    char* s;
    int size;
public:
    String(char*); // constructor
    ~String(); // destructor
};
 
String::String(char* c)
{
    size = strlen(c);
    s = new char[size + 1];
    strcpy(s, c);
}
String::~String() { 
    std::cout << "desturctor called" << std::endl;
    delete[] s; 
}

int main() {
    char s[] = "Hello world";
    String str(s);
}
```
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