有没有办法将派生类作为 if-else 语句中的条件传递?

我有一个虚拟函数，我想创建一个使用派生类作为条件的函数。因此，在下面的代码中，class Video_Games的变量shipcost为 4.99。等等电话，香肠和相册。如果有的话，我如何才能将类作为 if-else 语句中的条件传递，该语句位于名为"Package"的大类内的虚函数中？我想这样做，以便我可以在打印的收据中调用shipcost，该收据确切地知道如何显示每个类别的正确运输。

#include <iostream>
#include <string>
#include <iomanip>
#include <chrono>
#include <ctime>
using namespace std;
class Package
{
protected:
string name_and_address = "?";
double cost = 0.0;
double discount = 0.0;
double discount_rate = 0.0;
bool overnight_delivery = false;
bool insured = false;
string package_contents = "?";
double shipcost = 0.0;
public:
Package() {};
~Package() {};
protected:
virtual double calculate_cost() = 0;
virtual double shipping_cost()
{
if (class Video_Games :public Package) //getting error here that says class or struct definition is missing 
shipcost = 4.99;
else if (class Genius_Phone :public Package) //getting error here that says class or struct definition is missing 
shipcost = 25.00;
else if (class Sausage :public Package) //getting error here that says class or struct definition is missing 
shipcost = 9.00;
else
shipcost = 50.00;
return shipcost;
}
virtual double calculate_discount()
{
if (cost > 1000)
discount_rate = 0.033;
else if (cost > 500)
discount_rate = 0.028;
else if (cost > 200)
discount_rate = 0.024;
else
discount_rate = 0.019;
return cost * discount_rate;
}
friend ostream& operator<<(ostream &out, const Package &Package_Instance)
{
return Package_Instance.print(out);
}

ostream& print(ostream& out) const
{
chrono::system_clock::time_point now = chrono::system_clock::now();
time_t now_c = chrono::system_clock::to_time_t(now + chrono::hours(24));
chrono::system_clock::time_point now2 = chrono::system_clock::now();
time_t now2_c = chrono::system_clock::to_time_t(now2 + chrono::hours(72));
cout << "       *** BILL FOR GOODS ***n";
cout << "Customer: " << endl << endl;
cout << setprecision(2) << showpoint << fixed;
cout << name_and_address << endl;
cout << (overnight_delivery ? (put_time(localtime(&now_c), "Expected Arrival Date: %F")) : put_time(localtime(&now2_c), "Expected Arrival Date: %F")) << endl << endl;
cout << package_contents << endl;
cout << (insured ? "{INSURED}n" : "{NOT INSURED}n");
cout << (overnight_delivery ? "Expedited Shippingn" : "Standard Shippingn");
cout << shipcost << endl; //This is where I want the shipcost to display the dollar amount that corresponds directly to the type of shipcost used for each derived class. So video games would be 4.99, albums would be 50.00 etc. etc. etc. 
cout << "Total Cost is: $" << cost << endl;
cout << "Discount Percentage is: " << discount_rate * 100 << "%" << " for a discount of $" << discount << endl;
cout << "Total Cost after discount is $" << cost - discount << endl << endl;
return out;
}
};
class Video_Games :public Package
{
private:
int num_games = 0;
public:
Video_Games(string location, int number_of_games, bool express, bool insurance)
{
num_games = number_of_games;
name_and_address = location;
overnight_delivery = express;
insured = insurance;
package_contents = to_string(num_games) + " Video Game(s)";
cost = calculate_cost();
discount = calculate_discount();
shipcost = shipping_cost();
}
~Video_Games() {};
protected:
double calculate_cost()
{
cost = num_games * 19.99;
if (overnight_delivery) { cost += shipcost; } //this would be 4.99, and so and so forth for the rest of the classes (not edited yet, but I will edito those when I can nail this baby down). 
if (insured) { cost *= 1.06; }
return cost;
}
};
class Genius_Phone :public Package
{
private:
int num_phones = 0;
int num_cases = 0;
public:
Genius_Phone(string location, int number_of_phones, bool express, bool insurance, int number_of_cases)
{
num_phones = number_of_phones;
name_and_address = location;
overnight_delivery = express;
insured = insurance;
num_cases = number_of_cases;
package_contents = to_string(num_phones) + " Genius Phone(s), " +
(num_cases > 0 ? "and " + to_string(num_cases) + " cases " : "");
cost = calculate_cost();
discount = calculate_discount();
}
~Genius_Phone() {};
protected:
double calculate_cost()
{
cost = num_phones * 699.99 + num_cases * 24.99;
if (overnight_delivery) { cost += 25.00; }
if (insured) { cost *= 1.11; }
return cost;
}
};
class Sausage :public Package
{
private:
int num_Hot_Dogs = 0;
int num_Condiments = 0;
int num_Hot_Dog_Buns = 0;
public:
Sausage(string location, int hotdogs, bool express, bool insurance, int condiments, int buns)
{
num_Hot_Dogs = hotdogs;
name_and_address = location;
overnight_delivery = express;
insured = insurance;
num_Condiments = condiments;
num_Hot_Dog_Buns = buns;
package_contents = to_string(num_Hot_Dogs) + " Hot Dog(s), " +
(num_Condiments > 0 ? to_string(num_Condiments) + " Condiment(s) " : "") +
(num_Hot_Dog_Buns > 0 ? "and " + to_string(num_Hot_Dog_Buns) + " Hot Dog Bun(s) " : "");
cost = calculate_cost();
discount = calculate_discount();
}
~Sausage() {};
protected:
double calculate_cost()
{
cost = num_Hot_Dogs * 5.99 + num_Hot_Dog_Buns * 1.29 + num_Condiments * 0.79;
if (overnight_delivery) { cost += 9.00; }
if (insured) { cost *= 1.03; }
return cost;
}
};
class Albums :public Package
{
private:
int num_albums = 0;
int limited_edition = 0;
int signed_vinyl = 0;
public:
Albums(string location, int vinyls, bool express, bool insurance, int limited, int signature)
{
num_albums = vinyls;
name_and_address = location;
overnight_delivery = express;
insured = insurance;
limited_edition = limited;
signed_vinyl = signature;
package_contents = to_string(num_albums) + " Sia Vinyl Record(s), " +
(limited_edition > 0 ? to_string(limited_edition) + " Limited Edition Version(s) " : "") +
(signed_vinyl > 0 ? "and " + to_string(signed_vinyl) + " Signed by Sia herself " : "");
cost = calculate_cost();
discount = calculate_discount();
}
~Albums() {};
protected:
double calculate_cost()
{
cost = num_albums * 19.99 + signed_vinyl * 79.99 + limited_edition * 29.99;
if (overnight_delivery) { cost += 50.00; }
if (insured) { cost *= 1.25; }
return cost;
}
};
int main()
{
Video_Games a("Link LINKnKokiri ForestnKyoto, JAPAN 77547n", 4, true, false);
cout << a;
Genius_Phone b("Ada LOVELACEn1010 Binary StreetnLondon, ENGLAND 67859n", 1, true, false, 2);
cout << b;
Sausage c("Princess Annan2013 Disney RoadnArendelle, ALASKA 92684n", 350, false, true, 351, 4);
cout << c;
Albums d("David,n1326 90th Drive NEnEverett, WASHINGTON 98205n", 4, false, true, 2, 1);
cout << d;
return 0;
}