Destructor is a member function which destructs or deletes an object.

Syntax:

~constructor-name();

Properties of Destructor:

• Destructor function is automatically invoked when the objects are destroyed.
• It cannot be declared static or const.
• The destructor does not have arguments.
• It has no return type not even void.
• An object of a class with a Destructor cannot become a member of the union.
• A destructor should be declared in the public section of the class.
• The programmer cannot access the address of destructor.

When is destructor called?

A destructor function is called automatically when the object goes out of scope:
(1) the function ends
(2) the program ends
(3) a block containing local variables ends
(4) a delete operator is called

How destructors are different from a normal member function?

• Destructors have same name as the class preceded by a tilde (~)
• Destructors don’t take any argument and don’t return anything

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() { delete[] s; }

Can there be more than one destructor in a class?
No, there can only one destructor in a class with classname preceded by ~, no parameters and no return type.

When do we need to write a user-defined destructor?

If we do not write our own destructor in class, compiler creates a default destructor for us. The default destructor works fine unless we have dynamically allocated memory or pointer in class. When a class contains a pointer to memory allocated in class, we should write a destructor to release memory before the class instance is destroyed. This must be done to avoid memory leak.

Can a destructor be virtual?

Yes, In fact, it is always a good idea to make destructors virtual in base class when we have a virtual function. See virtual destructor for more details.