如何修复"Overloaded member function not found"错误？

我一直得到以下错误:

"overloaded function not found in 'pizza'"

指下面的void outputDescription和double computePrice函数。我不知道出了什么问题。

我是c++的初学者，但是代码看起来是正确的。这是上课用的。我应该至少有一个mutator函数和一个accessor函数，一个用来计算价格的函数和一个用来输出披萨描述的函数。

#include <iostream>
#include <string>
using namespace std;

class pizza
{
    public:
        void getOrder (string, string, int, int) ;
        void outputDescription (string&, string&, int&, int&) const;
        double computePrice (string&, int&, int&) const;
    private:
        string type;
        string size;
        int pepperoni;
        int cheese;
};
int main ()
{
    pizza customerpizza;
    double price;
    string type;
    string size;
    int pepperoni;
    int cheese;
    customerpizza.getOrder (type, size, pepperoni, cheese);
    customerpizza.outputDescription (type, size, pepperoni, cheese);
    price = customerpizza.computePrice (size, pepperoni, cheese);
    cout << "Total cost is $" << price << ".n";
    system("PAUSE");
    return 0;
}
void pizza::getOrder (string type, string size, int pepperoni, int cheese)
{
    int pizzaType;
    int pizzaSize;
    cout << "Please choose 1 for deep dish, 2 for hand tossed, or 3n";     cout << " for pan pizza.n";
    cin >> pizzaType;
    switch(pizzaType)
    {
        case 1: type = "deep dish";
        break;
        case 2: type = "hand tossed";
        break;
        case 3: type = "pan";
        break;
        default: cout << "You entered an invalid choice. Pleasen";              
                 cout << " enter 1 for deep dish, 2 for handn";             
                 cout << " tossed, or 3 for pan pizza.n";
    }
    cout << "Please choose 1 for small, 2 for medium, or 3 forn"; 
    cout << " large pizza.n";
    cin >> pizzaSize;
    switch(pizzaSize)
    {
        case 1: size = "small";
        break;
        case 2: size = "medium";
        break;
        case 3: size = "large";
        break;
        default: cout << "You entered an invalid choice. Pleasen";
                 cout << " enter 1 for small, 2 for medium, orn";
                 cout << " 3 for large pizza.n";
    }
    cout << "How many pepperoni servings on this pizza?n";
    cin >> pepperoni;
    cout << "How many cheese servings on this pizza?n";
    cin >> cheese;
}
void pizza::outputDescription (string type, string size, int pepperoni, int cheese) 
{
    cout << "You ordered a " << size << << type << " pizza with n"; 
    cout << pepperoni << " servings of pepperoni and "<< cheese << endl;   
    cout << "servings of cheese.n";
}
double pizza::computePrice (string size, int pepperoni, int cheese)
{
    double price;
    if (size = "small")
    {
        price = 10 + (2 * (pepperoni + cheese));
    }
    else if (size = "medium")
    {
        price = 14 + (2 * (pepperoni  + cheese));
    }
    else if (size = "large")
    {
        price = 17 + (2 * (pepperoni + cheese));
    }
    return price;
}