Destructors

“Destructor” functions are the inverse of constructor functions. They are called when objects are destroyed (deallocated). Designate a function as a class’s destructor by preceding the class name with a tilde (~). For example, the destructor for class String is declared: ~String().

The destructor is commonly used to “clean up” when an object is no longer necessary. Consider the following declaration of a String class:

#include <string.h>

class String

{

public:

    String( char *ch );  // Declare constructor

    ~String();           //  and destructor.

private:

    char *_text;

};

// Define the constructor.

String::String( char *ch )

{

    // Dynamically allocate the correct amount of memory.

    _text = new char[strlen( ch ) + 1];

    // If the allocation succeeds, copy the initialization string.

    if( _text )

       strcpy( _text, ch );

}

// Define the destructor.

String::~String()

{

    // Deallocate the memory that was previously reserved

    //  for this string.

    delete[] _text;

}

In the preceding example, the destructor String::~String uses the delete operator to deallocate the space dynamically allocated for text storage.