c++ - 错误信息 : non-static member found in multiple base-class subobjects of type person

Question

// Homework 3.cpp : Defines the entry point for the console application.
//

#include <iostream>
#include <string>
#include <iomanip>
#include <cassert>

using namespace std;

class Person{
public:
    Person(){ //Default Constructor
        name = "";
        ssn = 0;
        age = 0;
        gender = "";
        address = "";
        phone = "";
    }

    Person(const Person& p){ //copy constructor
        name = p.name;
        ssn = p.ssn;
        age = p.age;
        gender = p.gender;
        address = p.address;
        phone = p.phone;
    }

    Person(string _name, int _ssn, int _age, string _gender, string _address, string _phone)
    {
        name = _name;
        ssn = _ssn;
        age = _age;
        gender = _gender;
        address = _address;
        phone = _phone;
    }

    const string getName(){ return name; }
    const int getSSN(){ return ssn; }
    const int getAge(){ return age; }
    const string getGender(){ return gender; }
    const string getAddress(){ return address; }
    const string getPhone(){ return phone; }

    void setName(const string name);
    void setSSN(const int ssn);
    void setAge(const int age);
    void setGender(const string gender);
    void setAddress(const string address);
    void setPhone(const string phone);

protected:
    string name;
    int ssn;
    int age;
    string gender;
    string address;
    string phone;

};

class Student : public Person{
public:
    Student(){ //default
        gpa = 0;
        major = "";
        gradYear = 0;
    }

    Student(const Student& s) //copy
    {
        gpa = s.gpa;
        major = s.major;
        gradYear = s.gradYear;
    }

    Student(string _name, int _ssn, int _age, string _gender, string _address, string _phone, double _gpa, string _major, int _gradYear) : Person(_name, _ssn, _age, _gender, _address, _phone){
        gpa = _gpa;
        major = _major;
        gradYear = _gradYear;
    }


    const double getGPA(){ return gpa; }
    const string getMajor(){ return major; }
    const int getGradYear(){ return gradYear; }

    void setGPA(const double gpa);
    void setMajor(const string major);
    void setGradYear(const int gradYear);

protected:
    double gpa;
    string major;
    int gradYear;
};

class Employee : public Person{
public:
    Employee(){
        department = "";
        jobTitle = "";
        yearHire = 0;
    }

    Employee(const Employee& e){
        department = e.department;
        jobTitle = e.jobTitle;
        yearHire = e.yearHire;
    }

    Employee(string _name, int _ssn, int _age, string _gender, string _address, string _phone, string _department, string _jobTitle, int _yearHire) : Person(_name, _ssn, _age, _gender, _address, _phone){
        department = _department;
        jobTitle = _jobTitle;
        yearHire = _yearHire;
    }

    const string getDepartment(){ return department; }
    const string getJobTitle(){ return jobTitle; }
    const int getYearHire(){ return yearHire; }

    void setDepartment(const double department);
    void setJobTitle(const double jobTitle);
    void setYearHire(const double yearHire);


    virtual double getAnnualWages() = 0; // a pure virtual function.

protected:
    string department;
    string jobTitle;
    int yearHire;
};

class HourlyEmployee : public Employee{
public:
    HourlyEmployee(){
        hourlyRate = 0;
        hoursWorked = 0;
        unionDues = 0;

    }

    HourlyEmployee(const HourlyEmployee& he){
        hourlyRate = he.hourlyRate;
        hoursWorked = he.hoursWorked;
        unionDues = he.unionDues;
    }

    HourlyEmployee(string _name, int _ssn, int _age, string _gender, string _address, string _phone, string _department, string _jobTitle, int _yearHire, double _hourlyRate, double _hoursWorked, double _unionDues):Employee(_name, _ssn, _age, _gender, _address, _phone, _department, _jobTitle, _yearHire){
        hourlyRate = _hourlyRate;
        hoursWorked = _hoursWorked;
        unionDues = _unionDues;
    }

    const double getHourlyRate(){ return hourlyRate; }
    const double getHoursWorked(){ return hoursWorked; }
    const double getUnionDues(){ return unionDues; }

    void setHourlyRate(const double hourlyRate);
    void setHoursWorked(const double hoursWorked);
    void setUnionDues(const double unionDues);

    double getAnnualWages(){ return (hourlyRate*hoursWorked) + unionDues; }

protected:
    double hourlyRate;
    double hoursWorked;
    double unionDues;

};

class SalariedEmployee : public Employee{
public:
    SalariedEmployee(){ annualSalary = 0; }

    SalariedEmployee(const SalariedEmployee& se){
        annualSalary = se.annualSalary;
    }

    SalariedEmployee(string _name, int _ssn, int _age, string _gender, string _address, string _phone, string _department, string _jobTitle, int _yearHire, double _annualSalary):Employee(_name, _ssn, _age, _gender, _address, _phone, _department, _jobTitle, _yearHire)
    {
        annualSalary = _annualSalary;
    }

    double getAnnualSalary(){ return annualSalary; }

    void setAnnualSalary(const double annualSalary);

    double getAnnualWages(){ return annualSalary; }

protected:
    double annualSalary;

};

class StudentEmployee : public Student, public HourlyEmployee{ //multiple inheritance of student and HourlyEmployee
public:


    StudentEmployee(){}

    StudentEmployee(const StudentEmployee& ste){}

    StudentEmployee(string _name, int _ssn, int _age, string _gender, string _address, string _phone, string _department, string _jobTitle, int _yearHire, double _hourlyRate, double _hoursWorked, double _unionDues,double _gpa, string _major, int _gradYear): Student(_name, _ssn, _age, _gender, _address, _phone, _gpa, _major, _gradYear), HourlyEmployee(_name, _ssn, _age, _gender, _address, _phone, _department, _jobTitle, _yearHire, _hourlyRate, _hoursWorked, _unionDues){}



protected:
};

struct ListNode { //struct for list
    Person p;
    ListNode *link;
};

class SingleLinkedList{ //class to store all persons
public:
    SingleLinkedList() {
        front = rear = nullptr;
        size = 0;
    }

    ~SingleLinkedList() {
        Clear();
    }

    ListNode* headptr(){
        return front;
    }

    // Removes every node in the list.  Frees my memory with delete.
    void Clear() {
        ListNode *node = front;

        while (node != nullptr) {
            ListNode *next = node->link;
            delete node;
            node = next;
        }

        front = rear = nullptr;
        size = 0;
    }

    bool Contains(Person p) const {
        ListNode *node = front;

        while (node != nullptr) {
            if ( node->p.getName() == p.getName() && node->p.getSSN() == p.getSSN() && node->p.getAge() == p.getAge() && node->p.getGender() == p.getGender() && node->p.getAddress() == p.getAddress() && node->p.getPhone() == p.getPhone() ) { return true; } //checks to see if all of the information for the person is the same
            node = node->link;
        }

        return false;
    }

    void PopFront() {
        assert(size > 0);

        ListNode *obsolete = front;

        if (front == rear) { // Exactly one element in our list
            front = rear = nullptr;
        }
        else {
            front = obsolete->link;
        }

        delete obsolete;
        --size;
    }

    void PushBack(Person p) {
        ListNode *insert = new ListNode(); // We need to delete this node later
        insert->p = p;
        insert->link = nullptr;

        if (front == nullptr) {
            front = rear = insert;
        }

        rear->link = insert;
        rear = insert;
        ++size;
    }

    void PushFront(Person p) {
        ListNode *insert = new ListNode();
        insert->link = front; // This node will be the new front, connect the old front
        insert->p = p;

        if (front == nullptr) {  // No elements currently in the list
            front = rear = insert;
        }

        front = insert;
        ++size;
    }

    int Size() const {
        return size;
    }

    void displayNode(ListNode *ptr)const{
        cout << setw(3) << ptr->p.getName() << endl;
    }

    void displayList(ListNode *ptr)const{
        if (ptr==nullptr){
            cout << "Nothing to display!\n";
        }
        for (int i = 1; i <= size;i++){
            displayNode(ptr);
            ptr = ptr->link;
        }
    }

protected:
    int size;
    ListNode *front, *rear; // Front points to first node in list, rear to last
};








//main program
int main()
{
    Person a("John Doe", 123456789, 26, "male", "123 Park Pl", "555-123-4567");
    Person b("Jane Smith", 234567890, 21, "female", "66 Oak Ave", "123-456-7890");
    Student s("Katie Brown",749374394, 18,"female","100 Curtain Rd","472-473-2038", 4.0, "Statistics", 2016);
    SalariedEmployee se("Ross Gellar", 123056789, 55, "male", "123 5th Ave", "515-683-8924", "Science", "Professor", 1999, 50000);
    HourlyEmployee he("Monica Bing", 123056589, 55, "female", "64 South Park Dr", "538-238-0747", "Dining", "Chef", 1999, 20.00, 40, 100);
    StudentEmployee stuem("Cathrine Miller", 550789234, 25, "female", "218 Knickerbocker Way", "888-555-0000", "Fitness", "Trainer", 2015, 7.25, 10, 5, 3.2, "Computer Science", 2017);


    SingleLinkedList x;
    x.PushBack(a);
    x.PushBack(b);
    x.PushFront(s); //adds student f to the list of persons
    x.displayList(x.headptr());

    if (x.Contains(a) == true) //to show john doe is on list
        cout << "This " << a.getName() << " is in the list.\n";
    else
        cout << "This " << a.getName() << " is NOT in the list.\n";

    x.Clear(); //clears list

    x.displayList(x.headptr());

    if (x.Contains(a) == true) //shows john doe not on list because list was cleared
        cout << "This " << a.getName() << " is in the list.\n";
    else
        cout << "This " << a.getName() << " is NOT in the list.\n";


    cout<< "Annual Wages for "<<se.getName()<<" is "<<se.getAnnualWages()<<endl;
    cout<< "Annual Wages for "<<he.getName()<<" is "<<he.getAnnualWages()<<endl;
    cout<< "Annual Wages for "<<stuem.getName()<<" is "<<stuem.getAnnualWages()<<endl;


    return 0;
}

在最后一个 cout 语句中，我的程序将给我错误消息 non-static member 'getName' found in multiple base-class subobjects of type person。我知道我必须将所有变量都引用到一个基类中，但我不知道该怎么做

Answer 1

在这种情况下，您必须使用 Person 的 virtual 继承。我想这就是这个作业的重点。你遇到了 The Diamond problem ，因为在 stuem.getName() 中，编译器不知道要使用两个底层 Person 基类实例的哪个实例。

使继承虚拟 将确保只有一个Person 对象:

class Student : virtual public Person { ... };
class Employee : virtual public Person { ... };

题外话，但此时您应该使用成员初始化列表并将 "" 分配给已经初始化且为空的 std::string，嗯，看着不舒服。在 C++11 中可以默认复制构造函数:

Person(const Person& p) = default;