PRODUCT  :  Borland C++                           NUMBER  :  1553
  VERSION  :  3.x
       OS  :  DOS
     DATE  :  October 25, 1993                         PAGE  :  1/5

    TITLE  :  How to override freeItem for Collections




  //=============================================================
  //
  // Example of a derived TNSCollection class that can be used to
  // store objects that have their own destructors.
  //
  // IMPORTANT:
  //   When a TNSCollection item is deleted, the virtual member
  //   function freeItem() is called.  By default, this function
  //   simply deletes a void pointer.  This is fine for objects
  //   which do not have their own destructors.  For objects with
  //   destructors, freeItem MUST be overridden for proper
  //   clean-up.  To provide proper clean-up, the void pointer
  //   passed in to freeItem must be cast to the class type
  //   before deletion.
  //
  //=============================================================
  #define Uses_TCollection
  #define Uses_ipstream
  #define Uses_opstream
  #include <tv.h>
  #include <conio.h>
  #include <iostream.h>

  //=============================================================
  // TFruit class
  //    This is the object we'll put in the collection.
  //=============================================================
  class TFruit
  {

      static int refCount;
      char *name;

  public:

      TFruit( char *s )
      {
          name = newStr( s );
          ++refCount;
          cout << "  TFruit CTor: " << name << " (" << refCount
               << ")" << endl;
      }














  PRODUCT  :  Borland C++                           NUMBER  :  1553
  VERSION  :  3.x
       OS  :  DOS
     DATE  :  October 25, 1993                         PAGE  :  2/5

    TITLE  :  How to override freeItem for Collections




      ~TFruit()
      {
          cout << "!!TFruit DTor: " << name << " (" << refCount
               << ")" << endl;
          --refCount;
          delete name;
      }

  };

  int TFruit::refCount;


  //=============================================================
  // TFruitBowl
  //    This is the collection we'll be using.  It's got full
  //    stream support, except for registration in the stream
  //    manager database.
  //=============================================================
  class TFruitBowl : public TCollection
  {

  public:

      //
      //constructor
      //
      TFruitBowl( ccIndex aLimit, ccIndex aDelta ) :
          TCollection( aLimit, aDelta )
      {
          cout << "Creating TFruitBowl..." << endl;
      }

      //
      //destructor
      //
      ~TFruitBowl()
      {
          cout << "Destroying TFruitBowl." << endl;
      }

  private:
      virtual void freeItem( void *item )













  PRODUCT  :  Borland C++                           NUMBER  :  1553
  VERSION  :  3.x
       OS  :  DOS
     DATE  :  October 25, 1993                         PAGE  :  3/5

    TITLE  :  How to override freeItem for Collections




          {
            //
            //Cast item to a TFruit pointer and then delete
            //
            delete (TFruit *) item;
          }

      //
      //The following (streamableName, readItem, writeItem,
      //streamable constructor, const name and build) functions
      //are pure virtual in TCollection, so they must be
      //redefined.  These functions add 'streamability' to the
      //TFruitBowl class.
      //
      virtual const char *streamableName() const
          { return name; }
      virtual void *readItem( ipstream& ip )
          { return( new TFruit( ip.readString() )); }
      virtual void writeItem( void *item, opstream& op )
          { op.writeString( ((TFruit *) item)->name ); }

  protected:

      TFruitBowl( StreamableInit ) : TCollection(streamableInit)
          {}

  public:

      static const char * const near name;
      static TStreamable *build()
          { return new TFruitBowl( streamableInit ); }

  };

  //
  //Initilize the 'name' static variable
  //
  const char * const near TFruitBowl::name = "TFruitBowl";

  //
  //Overloaded insertion and extraction operators - for
  //streamability.
  //













  PRODUCT  :  Borland C++                           NUMBER  :  1553
  VERSION  :  3.x
       OS  :  DOS
     DATE  :  October 25, 1993                         PAGE  :  4/5

    TITLE  :  How to override freeItem for Collections




  inline ipstream& operator >> ( ipstream& is, TFruitBowl& cl )
      { return is >> (TStreamable&)cl; }
  inline ipstream& operator >> ( ipstream& is, TFruitBowl*& cl )
      { return is >> (void *&)cl; }

  inline opstream& operator << ( opstream& os, TFruitBowl& cl )
      { return os << (TStreamable&)cl; }
  inline opstream& operator << ( opstream& os, TFruitBowl* cl )
      { return os << (TStreamable *)cl; }


  //=============================================================
  // main
  //    Here we create a TFruitBowl and successive insert and
  //    remove TFruit objects from it.  At the end, we destroy
  //    the TFruitBowl (with TFruit still in it).  The calls to
  //    'cout' demonstrate the constructor and destructor calls
  //    that take place.
  //=============================================================
  int main()
  {
      TFruitBowl *bowl = new TFruitBowl( 10, 10 );

      cout << "Adding items to fruit collection." << endl;
      bowl->insert( new TFruit( "Apple" ));
      bowl->insert( new TFruit( "Orange" ));
      bowl->insert( new TFruit( "Peach" ));
      bowl->insert( new TFruit( "Kiwi" ));

      cout << "\nRemoving items from fruit collection." << endl;
      bowl->atFree( 3 );
      bowl->atFree( 1 );

      cout << "\nAdding more items to fruit collection." << endl;
      bowl->insert( new TFruit( "Pear" ));
      bowl->insert( new TFruit( "Grapes" ));

      cout << "\nDestroying fruit bowl and contents." << endl;
      TObject::destroy( bowl );

      cout << "\nPress any key to terminate"
              " (and possibly clear screen. :-(";














  PRODUCT  :  Borland C++                           NUMBER  :  1553
  VERSION  :  3.x
       OS  :  DOS
     DATE  :  October 25, 1993                         PAGE  :  5/5

    TITLE  :  How to override freeItem for Collections




      getch();
      return 0;
  }


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