#include <iostream>
using namespace std;

//（1）目的：多型Polymorphism，與動態繫結(dynamic binding)
//（2）三層類別關係
//Ball----Football-----Superfootball
//    ....Baseball
 
//father class 1 
class Ball
{
public:
	virtual void show()
	{
		cout<<"\nI am a Ball";	
	} 
};
//son class 2 
class Baseball : public Ball
{
public:
	void show()
	{
		cout<<"\nI am a Baseball";
	}
};

//son class 2
class Football : public Ball
{
public:
	void show()
	{
		cout<<"\nI am a Football. \t";
	}	
	virtual void price()
	{
		cout<<"price = 300 NT.";
	}	
}; 


//grandson class 3 
                  //繼承上一層 Football 
class Superfootball : public Football
{
public:
	void show()
	{
		cout<<"\nI am a Superfootball. \t";
	}	
	void price()
	{
		cout<<"price = 900 NT.";
	}
}; 

///////////////
int main(int argc, char** argv) {
	//1.多形
	Ball * a1[3];
	a1[0] = new Baseball;
	a1[0]->show();
	//I am a Baseball
	
	a1[1] = new Football;
	a1[1]->show();
	//I am a Football

	cout<<endl;
	a1[2] = new Superfootball;
	a1[2]->show();
	//I am a Superfootball
	//父類別，可以指揮，孫子類別 
	
	
	//2.動態繫結(dynamic binding)
	//新增：在『son類別Football，grandson類別Superfootball』都新增函數price()，但是父類別沒有price()
	//問題1：能否由父類別Ball指標變數，來指揮，子類別/孫子類別的price()
	//結果：==> 無法 
	Ball * a2 = new Football;
	//a2->price();
	//無法執行 
	
	//3.改善方法： 動態繫結(dynamic binding)
	//原理：把父類別Ball==> 動態繫結到 ==>子類別Football，就可以了
	//指令：dynamic_cast<Football*>(Ball指標) 
	
	cout<<endl<<"-----------------------"<<endl;
	//Baseball 子類別裡面沒有price()函數， 執行x->price()會出現錯誤 
	Baseball * x = new Baseball;
	//x->price(); 
	 
	cout<<endl<<"-----------------------"<<endl;
	//如何判別有沒有price()，若有就執行，沒有就忽略，而不會讓程式當掉，發生錯誤
	//方法：if(用動態繫結(dynamic binding)，來判別) 
	//範例： if(dynamic_cast<Football*>(a3[0]))  f3[0]->price();
	
	Ball * a3[3];
	a3[0] = new Baseball;
	a3[0]->show();
	Football * f3[3];	
	f3[0]= dynamic_cast<Football*>(a3[0]);
	if(f3[0])f3[0]->price();
	
	a3[1] = new Football;
	a3[1]->show();
	f3[1]= dynamic_cast<Football*>(a3[1]);
	if(f3[1])f3[1]->price();	

	a3[2] = new Superfootball;
	a3[2]->show();
	f3[2]= dynamic_cast<Football*>(a3[2]);
	if(f3[2])f3[2]->price();
	
	cout<<endl<<endl;
	cout<<endl<<"-----------------------"<<endl;
	//3.使用迴圈顯示全部子類別的函數（要用動態繫結去判別）
	Ball * a4[3];
	a4[0] = new Baseball; 
	a4[1] = new Football; 
	a4[2] = new Superfootball; 
	for(int i=0;i<3;i++)
	{	
		a4[i]->show();		
		//錯誤做法： 
		//如果用 Football * f4 = new Football; 答案不對 
		//Football * f4 = new Football;
		//I am a Baseballprice = 300 NT.
		//I am a Football.        price = 300 NT.
		//I am a Superfootball.   price = 300 NT.
		
		//正確做法： 
		Football * f4 = dynamic_cast<Football*>(a4[i]);
		if(f4)f4->price();
		//I am a Baseball
		//I am a Football.        price = 300 NT.
		//I am a Superfootball.   price = 900 NT.
	} 
	
	return 0;
}