c++ - Getting derived class from base method -

i have 3 classes entity, character , item. when

character * player = new character(qrectf(0, 0, 50, 50), "player", thescene); player->setvelocityx(30)->setattackpoint(10); 

the compiler tells error: 'class entity' has no member named 'setattackpoint'. how can make entity* setvelocityx(qreal vx); return character pointer or item pointer?

.

class entity : public qobject, public qgraphicspolygonitem {     q_object      public:         entity();         entity(qreal x, qreal y, qreal w, qreal h, qstring tag, qgraphicsscene *scene = 0, qgraphicsitem *parent = 0);         entity(qrectf position, qstring tag, qgraphicsscene *scene = 0, qgraphicsitem *parent = 0);         entity(qstring tag, qgraphicsscene *scene = 0, qgraphicsitem *parent = 0);         entity* setvelocityx(qreal vx);         // etc }   class character : public entity {     q_object      public:         character(qreal x, qreal y, qreal w, qreal h, qstring tag, qgraphicsscene *scene = 0, qgraphicsitem *parent = 0);         character(qrectf position, qstring tag, qgraphicsscene *scene = 0, qgraphicsitem *parent = 0);         character(qstring tag, qgraphicsscene *scene = 0, qgraphicsitem *parent = 0);         character* setattackpoint(int attackpoint);         //etc }   class item : public entity {     q_object      public:         enum itemtype{             consummable,             special,             weapon         };          item(qstring name, qreal x, qreal y, qreal w, qreal h,  qstring tag = "item", qgraphicsscene *scene = 0, character *parent = 0);         item* setowner(character* newowner);         //etc } 

if absolutely on type (otherwise use dynamic_cast , check resulting pointer non-nullptr):

reinterpret_cast< character * >( player->setvelocityx(30))->setattackpoint(10) 

also, based on code, couldn't go instead or order of function calls significant?

player->setattackpoint(10)->setvelocityx(30)