C++链式继承

Question

我正在尝试为具有 3 个继承类(PersonData -> CustomerData -> PreferredCustomer)的超市创建百分比储蓄程序。整个程序必须遵循这个 UML 图:

我在第三节课上遇到了问题；特别是在类的第一个构造函数中初始化值。我在 Visual Studio 中收到一条错误消息:“形式参数 Pa 的重新定义”和“形式参数“dl”的重新定义”。

这是有错误的构造函数:

PreferredCustomer(string aLname, string aFname, string aAddress, 
        string aCity, string aState, int aZip, string aPhone, int cn, 
        bool ml, double Pa, double dl)   // constructor 1
{
    double Pa;
    double dl;
}

第三个子构造函数中的参数已从父构造函数重载。参数cn、ml、Pa、dl都被添加到这个参数中。

我不确定为什么会收到这些错误？另外，我应该创建一个虚函数还是使用指针？感谢您的帮助。

我的程序源码(供引用):

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

class PersonData // PersonData parent class defined
{
private:
    string lastName;
    string firstName;
    string address;
    string city;
    string state;
    string phone;
    int zip;

public:
    PersonData() // Default Constructor initialization
    {
        lastName = " ";
        firstName = " ";
        address = " ";
        city = " ";
        state = " ";
        zip = 0;
        phone = " ";
    }

    PersonData(string aLname, string aFname, string aAddress, string aCity, string aState, int aZip, string aPhone) // Constructor 1
    {
        lastName = aLname;
        firstName = aFname;
        address = aAddress;
        city = aCity;
        state = aState;
        zip = aZip;
        phone = aPhone;
    }

    // Accesor Functions
    string getLastName() const
    {
        return lastName;
    }

    string getFirstName() const
    {
        return firstName;
    }

    string getAddress() const
    {
        return address;
    }

    string getCity() const
    {
        return city;
    }

    string getState() const
    {
        return state;
    }

    int getZip() const
    {
        return zip;
    }

    string getPhone() const
    {
        return phone;
    }

    // Mutator Functions
    void setLastName(string aLname)
    {
        lastName = aLname;
    }

    void setFirstName(string aFname)
    {
        firstName = aFname;
    }

    void setAddress(string aAddress)
    {
        address = aAddress;
    }

    void setCity(string aCity)
    {
        city = aCity;
    }

    void setState(string aState)
    {
        state = aState;
    }

    void setZip(int aZip)
    {
        zip = aZip;
    }

    void setPhone(string aPhone)
    {
        phone = aPhone;
    }
};

class CustomerData :public PersonData // CustomerData child class of PersonData base class
{
private:
    int customerNumber;
    bool mailingList;

public:
    CustomerData() // Default constructor
    {
        customerNumber = 0;
        mailingList = 0;
    }

    CustomerData(int cNum, bool mailL) // Constructor 1
    {
        setCustomerNumber(cNum);
        setMailingList(mailL);
    }

    // Accessor Functions for child class
    int getCustomerNumber() const
    {
        return customerNumber;
    }

    bool getMailingList() const
    {
        if (mailingList != 0)
        {

            cout << "On Mailing List!: ";
            return mailingList;
        }

        else (mailingList == 0);
        {
            cout << "Not on mailing list!: ";
            return mailingList;
        }
    }

    // Mutator Functions for child class
    void setCustomerNumber(int cNum)
    {
        customerNumber = cNum;
    }

    void setMailingList(bool mailL)
    {
        mailingList = mailL;
    }
};

class PreferredCustomer :public CustomerData // child class of CustomerData child class
{
private:
    double purchasesAmount;
    double discountLevel;
public:

    PreferredCustomer() // default constructor
    {
            purchasesAmount = 0;
            discountLevel = 0;
    }

    PreferredCustomer(string aLname, string aFname, string aAddress, 
        string aCity, string aState, int aZip, string aPhone, int cn, 
        bool ml, double Pa, double dl)   // constructor 1
    {
        double Pa;
        double dl;
    }

    // Mutator Functions
    void setPurchasesAmount(double Pa)
    {
        purchasesAmount = Pa;
    }

    // Accessor Functions
    double getPurchasesAmount() const
    {
        return purchasesAmount;
    }

    double getDiscountLevel() const
    {
        return discountLevel;
    }

    void addPurchase(double P) const
    {

    }
};

int main()
{
    CustomerData Cdata;       // for access of child class functions
    PersonData Pdata;         // for access of parent class functions
    PreferredCustomer PCdata; // for access of preferred customer class functions
    string     temp1;         // Temporary variable for string values
    int        temp2,         // Temporary variable for integer values
        max = 100,            // For-loop maximum loop value
        i;                    // i variable
    bool       temp3;         // Temporary variable for bool values

    for (i = 1; i <= max; i++)
    {
        // Input Data
        cout << "Please input first Name: ";
        getline(cin, temp1);
        Pdata.setFirstName(temp1);

        cout << "Please input last Name: ";
        getline(cin, temp1);
        Pdata.setLastName(temp1);

        cout << "Please input address: ";
        getline(cin, temp1);
        Pdata.setAddress(temp1);

        cout << "Please input city: ";
        getline(cin, temp1);
        Pdata.setCity(temp1);

        cout << "Please input state: ";
        getline(cin, temp1);
        Pdata.setState(temp1);

        cout << "Please input Zip code: ";
        cin >> temp2;
        Pdata.setZip(temp2);

        cin.ignore(); // discards unread char from cin

        cout << "Please input Phone Number: ";
        getline(cin, temp1);
        Pdata.setPhone(temp1);

        cout << "Enter 1 to be included in mail list," << endl;
        cout << "Enter 0 to not be included in mail list: ";
        cin >> temp3;
        Cdata.setMailingList(temp3);

        Cdata.setCustomerNumber(i); // set customer number

        cout << endl << endl;

        cout << "Name: " << Pdata.getFirstName() << ", " << Pdata.getLastName() << " \n";
        cout << "Customer Number: " << Cdata.getCustomerNumber() << "\n";
        cout << "Address: " << Pdata.getAddress() << "\n";
        cout << "City: " << Pdata.getCity() << "\n";
        cout << "State: " << Pdata.getState() << "\n";
        cout << "Phone: " << Pdata.getPhone() << "\n";
        cout << "Zip: " << Pdata.getZip() << "\n";
        cout << Cdata.getMailingList() << "\n";

        cout << endl << endl;
        cin.ignore(); // discards unread char from cin
    }

    char c;
    cin >> c;

    return 0;
}

Answer 1

构造函数的目的是获取传入的参数并根据类声明构造对象并适本地初始化成员。它不仅需要初始化类，还需要初始化所有基类，这可以通过将参数传递给基类构造函数来完成。

在

PreferredCustomer(string aLname, string aFname, string aAddress, 
            string aCity, string aState, int aZip, string aPhone, int cn, 
            bool ml, double Pa, double dl)   // constructor 1
{
    double Pa;
    double dl;
}

1. 你没有初始化任何东西
2. 您正在声明两个与传入的参数匹配(或冲突)的局部参数

3. 您不调用基础的构造函数(大部分工作是如何完成的)

   PreferredCustomer(...) :CustomerData(...)

   客户数据(...) :PersonData(...)

4. 你不初始化这个类的成员

   purchasesAmount = pa;
   discountLevel = dl;