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To reclaim the memory in a class-object character array, you take advantage of what are called destructor functions, which are member functions that run when the memory for a class object is reclaimed.
Like that of a constructor, the name of the destructor is based on the name
of the class, but unlike the constructor name, the destructor name includes
a tilde prefix. The following, for example, is the railroad_car
class, augmented with a destructor that reclaims memory from the
serial_number array:
class railroad_car {
public: char *serial_number;
// Constructors:
railroad_car ( ) { }
railroad_car (char *input_buffer) {
// Create new array just long enough:
serial_number = new char[strlen(input_buffer) + 1];
// Copy string into new array:
strcpy (serial_number, input_buffer);
}
// Destructor:
~railroad_car ( ) {
cout << "Deleting a railroad serial number" << endl;
delete [ ] serial_number;
}
// Other:
virtual char* short_name ( ) {return "rrc";}
virtual double capacity ( ) {return 0.0;}
};
Note that, when you use the delete operator to reclaim an
array of objects, rather than an individual object, you place two brackets,
[ ], between the delete operator and the array name.
Because C++ keeps track of the lengths of all arrays created by the
new operator, C++ can proceed to reclaim all the memory in such an
array.