Examples of inheritance and polymorphism for C + + classes

Examples of inheritance of classes:

As an example of the production of the above dynamic Milky Way galaxy, suppose we define a class of stars as follows:

classStar{ Public: Star () {}~Star () {}      voidInit ();     voidMove ();  protected:     voidDraw ();     voidNewpos ();     voidRemove ();      Doublem_x =0;     intm_y;     DoubleM_step;     intM_color; };  voidStar::init () {     if(m_x = =0)     {m_x = rand ()%Screen_width;     }     Else     {m_x =0;     }m_y = rand ()%Screen_height;M_step = (rand ()% the) /1000.0+1;M_color = (int) (M_step *255/6.0+0.5);//the faster the speed, the brighter the colorM_color =RGB (M_color, M_color, m_color); }  voidStar::move () { Remove ();  Newpos ();  Draw (); }  voidStar::D Raw () {Putpixel ((int) m_x, m_y, m_color); }  voidStar::newpos () {M_x + =M_step;     if(M_x >screen_width)          This-Init (); }  voidStar::remove () {Putpixel ((int) m_x, M_y,0); }

Next we are asked to make a rectangular star what we should do, in fact, the rectangular star and the above difference is the draw () and Romove () These two functions, so we can use the method of class inheritance, and then use the same function name override method to write the class, there are three ways to inherit the following table is shown:

Derivation method	Public members of the base class	Protected members of the base class	Private member of base class	Summary of changes in access properties caused by derivation
Private derivation	becomes Private member	becomes Private member	Not visible	A non-private member in a base class becomes a private member in a derived class
Protected derivation	Become a protected member	becomes Private member	Not visible	Non-private members in a base class have a lower level of access properties in the derived class
Public derivation	is still public member	Still a member of protected	Not visible	The Access property of a non-private member in a base class in a derived class remains the same

So here we take the public inheritance, just change the class method in it (here we note that the data in the base class is not private type, because if the private class is not inherited in any way it is not callable, even if it is overloaded with a function with the same name):

 classRectstar: PublicStar {  Public: Rectstar () {}~Rectstar () {}      voidMove ()     { Remove (); Newpos (); Draw ();     }  protected:     voidDraw ();     voidRemove (); };   voidRectstar::D Raw () { Setfillcolor (m_color);FillRectangle (m_x, m_y, m_x +3, M_y +3); }  voidRectstar::remove () {Clearrectangle (m_x, m_y, m_x +4, M_y +3);}

Examples of inheritance and polymorphism for C + + classes