如何在 C++ 中的同一函数中使用字符串和双精度数

Posted 2023-02-22

【中文标题】如何在 C++ 中的同一函数中使用字符串和双精度数

【英文标题】：How to use strings and doubles in the same function in C++

【发布时间】：2018-11-02 01:18:10

【问题描述】：

对于一个班级项目，我需要在一个函数中获取客户的所有信息（包括他们的姓名、房间号等），因此我需要在同一个函数中使用双精度数和字符串。如果没有，是否有这样做或替代方法？

项目希望我们通过引用传递值。

//Prints a statement for each overnight customer.

#include <iostream>
#include <string>
#include <math.h>
#include <iomanip>
using namespace std;

const double sales_tax_rate = 0.055;

//Function prototypes
string customerInformation(string &customer_name, string &date_of_bill, 
string &hotelormotel_name, double &room_rate, double &number_of_nights, 
double &phone_charges, double &room_number);

int main()

    string customer_name, dummy, date_of_bill, hotelormotel_name;
    double room_rate = 0;
    double number_of_nights = 0;
    double phone_charges = 0;
    double room_number = 0;
    double room_cost;
    double subtotal;
    double total;
    double taxes;
    int counter = 1;
    char repeat;

    do
    
        counter += 1;
        taxes = 0;
        total = 0;
        subtotal = 0;
        room_cost = 0;

        customerInformation(customer_name, room_rate, number_of_nights, 
        phone_charges, room_number, date_of_bill, hotelormotel_name);

        room_cost = room_rate * number_of_nights;
        taxes = sales_tax_rate * room_cost;
        subtotal = taxes + room_cost;
        total = subtotal + phone_charges;

        cout << hotelormotel_name << endl << endl;
        cout << "Date:             " << date_of_bill << endl;
        cout << "Customer's Name:  " << customer_name << endl;
        cout << "Room Number:      " << room_number << endl;
        cout << "Number of Nights: " << number_of_nights << endl;
        cout << setprecision(2) << fixed << endl;
        cout << "Room Rate:     $" << room_rate << endl;
        cout << "Room Cost:     $" << room_cost << endl;
        cout << "Taxes:         $" << taxes << endl;
        cout << "Subtotal:      $" << subtotal << endl << endl;
        cout << "Phone Charges: $" << phone_charges << endl << endl;
        cout << "TOTAL DUE:     $" << total << endl << endl;
        cout << "Thank you for staying at " << hotelormotel_name << "!" << 
        endl;
        cout << "Drive safely and please come again!" << endl << endl;

        cout << "Would you like to run this program again? (Y or N): ";
        cin >> repeat;
        getline(cin, dummy);
        cout << endl;
     while (repeat == 'Y' || repeat == 'y');


string customerInformation(string &customer_name, string &date_of_bill, 
string &hotelormotel_name, double &room_rate, double &number_of_nights, 
double &phone_charges, double &room_number)

    cout << "Please enter the following information: " << endl;
    cout << "Hotel/Motel Name: ";
    getline(cin, hotelormotel_name);
    cout << "Customer Name:    ";
    getline(cin, customer_name);
    cout << "Date:             ";
    getline(cin, date_of_bill);
    cout << "Room Number:      ";
    cin >> room_number;

    do
    
        cout << "Number of Nights: ";
        cin >> number_of_nights;
        if (number_of_nights <= 0)
             cout << "Error: Invalid data entered, please try again.\n";
     while (number_of_nights <= 0);

    cout << endl;

    do
    
        cout << "Room Rate:     $";
        cin >> room_rate;
        if (room_rate <= 0)
            cout << "Error: Invalid data entered, please try again.\n";
     while (room_rate <= 0);

    do
    
        cout << "Phone Charges: $";
        cin >> phone_charges;
        if (phone_charges < 0)
            cout << "Error: Invalid data entered, please try again.\n";
     while (phone_charges < 0);

    cout << endl;

     return date_of_bill, customer_name, room_number, room_rate, 
number_of_nights, phone_charges, hotelormotel_name;

【问题讨论】：

你的程序怎么没有做你想做的事？您的函数是否已经同时接受字符串和双精度数？

每次我运行它我都会得到这个错误：错误 C2664 'std::string customerInformation(std::string &,std::string &,std::string &,double &,double & ,double &,double &)': 无法将参数 2 从 'double' 转换为 'std::string &' Project1 c:\users\worth\downloads\lab8-1-wortham.cpp 39

等你想返回所有这些东西吗？你不需要。您通过 通过引用 传递它们，这意味着如果您在函数中更改它们的值，这些更改将传回给调用者。不要将它们全部添加到 return 语句中。

请阅读the help pages，尤其是"What topics can I ask about here?"和"What types of questions should I avoid asking?"。还有take the tour 和read about how to ask good questions 和this question checklist。并了解如何创建Minimal, Complete, and Verifiable Example。

我也收到很多错误，例如：错误（活动）E0434 类型“double &”（非 const 限定）的引用无法使用“std::string”类型的值初始化Project1 C:\Users\worth\Downloads\Lab8-1-Wortham.cpp 39

【参考方案1】：

为什么不创建一个包含所有这些信息的结构？

   struct customerinfo 
   string customer_name;
   string date_of_bill;
   string hotelormotel_name;
   double room_rate;
   double number_of_nights; 
   double phone_charges; 
   double room_number;
   ;

然后你从类型结构返回一个变量。

【参考方案2】：

是的，还有一种使用结构体的替代方法，您可以按照以下方式创建自己的结构体

struct customerInfo  
      string customer_name, dummy, date_of_bill, hotelormotel_name;
      double room_rate;
      double number_of_nights;
      double phone_charges;
      double room_number;
      double room_cost;
      double subtotal;
      double total;
      double taxes;
;

然后您可以将结构类型的对象传递给函数，如下所示

//Function prototypes
string customerInformation(customerInfo tempCustomer);

你可以使用这个 tempCustomer 如下

string customerInformation(customerInfo tempCustomer)
         cin>>tempCustomer.customer_name;
         //you can call all attributes and assign them values accordingly
         //to return a particular value you can do
         return tempCustomer.customer_name;

【讨论】：

从这个方法你可以返回一个完整的对象（通过将函数的返回类型从字符串更改为customerInfo）。