c++ - 继承 - 不同的文件 (C++)

Question

我正在不同的文件 .h 和 .cpp 中尝试这个继承教程。

我已经完成了必要的头文件#include。当我尝试运行它时，我无法弄清楚代码有什么问题。它有错误说明:

严重性代码描述项目文件行

Error   C2011   'Person': 'class' type redefinition     
Error   C2027   use of undefined type 'Person'      
Error   C2065   'idNum': undeclared identifier  
Error   C2065   'lastName': undeclared identifier   
Error   C2065   'firstName': undeclared identifier      
Error   C2027   use of undefined type 'Person'      
Error   C2065   'idNum': undeclared identifier  
Error   C2065   'firstName': undeclared identifier      
Error   C2065   'lastName': undeclared identifier   

下面是我的代码:

Person.h

#include <iostream>
#include <string>

using namespace std;
class Person {

private:
    int idNum;
    string lastName;
    string firstName;
public:
    void setFields(int, string, string);
    void outputData();


};

void Person::setFields(int num, string last, string first) {
    idNum = num;
    lastName = last;
    firstName = first;

}

void Person::outputData()
{
    cout << "ID #" << idNum << " Name: " << firstName << " " << lastName << endl;
}

Customer.h

#include <iostream>
#include <string>
#include "Person.h"

using namespace std;
class Customer :public Person
{

private:
    double balanceDue;
public:
    void setBalDue(double);
    void outputBalDue();
};

void Customer::setBalDue(double bal) {
    balanceDue = bal;
}

void Customer::outputBalDue() {
    cout << "Balance due $ " << balanceDue << endl;
}

main.cpp

#include <iostream>
#include <string>
#include "Customer.h"
#include "Person.h"

using namespace std;

int main() {
    Customer cust;
    //cust.setFields(215, "Santini", "Linda");
    //cust.outputData();
    cust.setBalDue(147.95);
    cust.outputBalDue();

    return 0;

}

编辑:Person.h

#include <iostream>
#include <string>
#ifndef PERSON_H
#define PERSON_H

using namespace std;
class Person {

private:
    int idNum;
    string lastName;
    string firstName;
public:
    void setFields(int, string, string);
    void outputData();


};

void Person::setFields(int num, string last, string first) {
    idNum = num;
    lastName = last;
    firstName = first;

}

void Person::outputData()
{
    cout << "ID #" << idNum << " Name: " << firstName << " " << lastName << endl;
}
#endif

Answer 1

函数定义应该在 .cpp 文件中，而不是在 .h 文件中。

你需要这个:

客户.cpp

#include <iostream>
#include <string>
#include "Customer.h"

using namespace std;

void Customer::setBalDue(double bal) {
    balanceDue = bal;
}

void Customer::outputBalDue() {
    cout << "Balance due $ " << balanceDue << endl;
}

main.cpp

#include <iostream>
#include <string>
#include "Customer.h"
#include "Person.h"

using namespace std;

int main() {
    Customer cust;
    //cust.setFields(215, "Santini", "Linda");
    //cust.outputData();
    cust.setBalDue(147.95);
    cust.outputBalDue();

    return 0;    
}

Person.cpp

#include <iostream>
#include <string>
#include "Person.h"

void Person::setFields(int num, string last, string first) {
    idNum = num;
    lastName = last;
    firstName = first;    
}

void Person::outputData()
{
    cout << "ID #" << idNum << " Name: " << firstName << " " << lastName << endl;
}

在头文件中你需要include guards .

Customer.h

#ifndef _customer_inc_h_
#define _customer_inc_h_  // Include guard. This makes sure that
                          // Customer.h is included actually only once
                          // to avoid "multiple definition" errors

#include <iostream>
#include <string>
#include "Person.h"

using namespace std;

class Customer :public Person
{

private:
    double balanceDue;
public:
    void setBalDue(double);
    void outputBalDue();
};

#endif

Person.h

#ifndef _person_inc_h_
#define _person_inc_h_

#include <iostream>
#include <string>

using namespace std;

class Person {

private:
    int idNum;
    string lastName;
    string firstName;
public:
    void setFields(int, string, string);
    void outputData();
};
#endif