c++ - Polymorphism, Downcasting, and Virtual Functions -


i have code changing class more object-oriented c++ class, ie: less calls inside main loop.

class shape abstract  { public:     virtual bool check_collision(sdl_point);     virtual bool check_collision(sdl_rect);     virtual bool check_collision(shape&); protected: };  class adv_object : public object { public:     adv_object(shape *obj);     virtual void set_shape(shape* obj) { prec_area = obj; }     virtual bool check_collision(sdl_point);     virtual bool check_collision(sdl_rect);     virtual bool check_collision(shape&); protected:     shape* prec_area; //better area determination };

where shape purely abstract class, , inherited class, ie: circle.

class circle : public shape {   public:    void check_collision(sdl_point) override;    void check_collision(sdl_rect) override;    void check_collision(shape&) override; };

when circle downcasted shape, overloads of virtual functions called or abstract functions called instead?

the program use run-time information (so-called "virtual table") determine virtual function call. done total disregard down/up-casting, in other words - correct overloaded function called.

as side note - if want call specific "incarnation" of virtual function you'd have use explicit name resolution, this:

shape * c = new circle; c->square::check_collision(...); // hope see issues maycause

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