Object-Oriented Programming In C++: Destructor

Submitted by PhoeniciansSy on Friday, September 12, 2014 - 06:21.

Is a member function in the class, which has the following characteristics: 1. It has the same name as the class preceded with a tilde '~'. For example, the destructor for class Time is declared: ~Time() 2. It doesn't return any type. 3. It is called when objects are destroyed to release all allocated resources. 4. There is just one destructor in a class, it can not be overloaded.

When Constructors and Destructors are Called:

They are called dynamically and that depends on the scope of objects.

Global Scope Objects:

The constructor is called dynamically before any other function even the main function, and the destructor is called dynamically at the end of the main function.

Local Scope Objects:

The constructor is called dynamically when the object is defined, and the destructor is called dynamically at the end of the block of statements where the object is defined. Example:

// Definition of class CreateAndDestroy.
class CreateAndDestroy 
{
    public:
        CreateAndDestroy( int value)  // constructor
        {
             data = value;
             cout << "Object " << data << " constructor";        
        }
        ~CreateAndDestroy()  // destructor
        {
             cout << "Object " << data << " destructor " << endl; }
        }
    private:
        int data;
};
 
void create( void );  // prototype
 
CreateAndDestroy first( 1 );  // global object
 
int main()
{
    cout << " (global created before main)" << endl;
 
    CreateAndDestroy second( 2 );  // local object
    cout << " (local in main)" << endl;
 
    create();  // call function to create objects
    CreateAndDestroy fourth( 4 );  // local object
    cout << " (local in main)" << endl;
    return 0;
}
 
// Function to create objects
void create( void )
{
    CreateAndDestroy fifth( 5 );
    cout << " (local in create)" << endl;
 
    CreateAndDestroy seventh( 7 );
    cout << " (local in create)" << endl;
}

The Output:

Object 1 constructor (global created before main) Object 2 constructor (local in main) Object 5 constructor (local in create) Object 7 constructor (local in create) Object 7 destructor Object 5 destructor Object 4 constructor (local in main) Object 4 destructor Object 2 destructor Object 1 destructor

Note: You can find the full source code of this example in code.zip file.