在线银行C++项目编译错误：类型限定符不兼容与抽象类实例化问题

错误1：对象的类型限定符与成员函数Customer::displayCustomer不兼容 #

原因 #

Account::displayAccount()是const成员函数，在该函数中成员变量user会被视为const Customer类型。但Customer::displayCustomer()未声明为const成员函数，const对象无法调用非const成员函数，导致类型不兼容。

修复方案 #

修改Customer类的displayCustomer()方法，将其声明并定义为const成员函数：

修改后的Customer.h

#ifndef CUSTOMER_H
#define CUSTOMER_H

#include <string>

class Customer {
public:
    Customer();
    Customer(const std::string& firstName, const std::string& lastName, const std::string& address, const std::string& email);
    void displayCustomer() const; // 添加const修饰符

private:
    std::string firstName;
    std::string lastName;
    std::string address;
    std::string email;
};

#endif // CUSTOMER_H

修改后的Customer.cpp

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

Customer::Customer() {
    // 默认构造函数
}

Customer::Customer(const std::string& firstName, const std::string& lastName, const std::string& address, const std::string& email)
    : firstName(firstName), lastName(lastName), address(address), email(email) {
    // 重载构造函数
}

void Customer::displayCustomer() const { // 添加const修饰符
    std::cout << "Name: " << firstName << " " << lastName << std::endl;
    std::cout << "Address: " << address << std::endl;
    std::cout << "Email: " << email << std::endl;
}

错误2：不允许抽象类类型SavingsAccount的对象 #

原因 #

基类Account包含两个纯虚函数：virtual bool deposit(double amount) = 0;和virtual bool withdraw(double amount) = 0;。继承自Account的子类必须实现这两个纯虚函数，否则子类会被标记为抽象类，无法实例化对象。当前SavingsAccount未实现这两个函数，因此触发编译错误。

修复方案 #

在SavingsAccount类中添加deposit和withdraw函数的声明与实现：

修改后的SavingsAccount.h

#ifndef SAVINGSACCOUNT_H
#define SAVINGSACCOUNT_H

#include "Account.h"

class SavingsAccount : public Account {
public:
    SavingsAccount();
    SavingsAccount(int accountNumber, double balance, const Customer& user, double interestRate);
    double getInterestRate() const;
    double calcInterest();
    bool deposit(double amount) override; // 添加函数声明
    bool withdraw(double amount) override; // 添加函数声明
    void displayAccount() const override;

private:
    double interestRate;
};

#endif // SAVINGSACCOUNT_H

修改后的SavingsAccount.cpp

#include "SavingsAccount.h"
#include <iostream>
#include <iomanip>

SavingsAccount::SavingsAccount()
    : interestRate(0.02) {
    // 默认构造函数
}

SavingsAccount::SavingsAccount(int accountNumber, double balance, const Customer& user, double interestRate)
    : Account(accountNumber, balance, user), interestRate(interestRate) {
    // 重载构造函数
}

double SavingsAccount::getInterestRate() const {
    return interestRate;
}

double SavingsAccount::calcInterest() {
    double interest = getBalance() * interestRate;
    setBalance(getBalance() + interest);
    return interest;
}

bool SavingsAccount::deposit(double amount) {
    if (amount >= 0) {
        setBalance(getBalance() + amount);
        return true;
    }
    return false;
}

bool SavingsAccount::withdraw(double amount) {
    if (amount >= 0 && amount <= getBalance()) {
        setBalance(getBalance() - amount);
        return true;
    }
    return false;
}

void SavingsAccount::displayAccount() const {
    std::cout << "Savings Account ----" << std::endl;
    Account::displayAccount();
    std::cout << "Interest rate: " << interestRate * 100 << "%" << std::endl;
}

完成上述修改后，两处编译错误即可解决。

内容的提问来源于stack exchange，提问作者gbolive011