29 The Power of Inheritance and Polymorphism

Implementation: DungeonItems 1057ActiveItemThe constructor for class ActiveItem again just initializes some data members tozero after passing the given arguments to the DungeonItem constructor. FunctionActiveItem::Read() is similar to Collectable::Read() in that it invokes theDungeonItem::Read() function then reads the extra data values (fHealth andfStrength).There are a couple of trivial functions (GetHit() { fHealth -= damage; };and Alive() { return fHealth > 0; }). The Move() operation involves callsto the (inherited) Erase() and Draw() functions. Function Step() works out thex, y offset (+1, 0, or -1) coordinates of a chosen neighboring Pt.void ActiveItem::Move(const Pt& newpoint){Erase();fPos.SetPt(newpoint);Draw();}Pt ActiveItem::Step(int dir){Pt p;switch(dir) {case 1: p.SetPt(-1,1); break;case 2: p.SetPt(0,1); break;case 3: p.SetPt(1,1); break;case 4: p.SetPt(-1,0); break;case 6: p.SetPt(1,0); break;case 7: p.SetPt(-1,-1); break;case 8: p.SetPt(0,-1); break;case 9: p.SetPt(1,-1); break;}return p;}PlayerThe constructor for class Player passes its arguments to its parents constructor andthen sets its data members to 0 (NULL for the pointer members). The Read()function is similar to Collectable::Read(); it invokes the inherited DungeonItem::Read() and then gets the extra "manna" parameter.The first call to ShowStatus() creates the NumberItem and EditText windowsand arranges for their display. Subsequent calls update the contents of theNumberItem windows if there have been changes (the call to SetVal() results inexecution of the NumberItem object's ShowContents() function so resulting inchanges to the display).void Player::ShowStatus(){if(fWinH == NULL) {