带有文件流错误的 C++ Void 函数

Question

我正在尝试编写一个代码，它接受一个输入文件并组织它并计算一些值。但是，我的 getName 函数有问题，如果读取 -1，该函数应该通过使用 get 成员函数对输入文件中的字符求和来分配名字和姓氏以通过引用参数调用。以下是代码的错误参数:

main.cpp:7:14: error: variable or field 'getName' declared void
main.cpp:7:14: error: 'ifstream' was not declared in this scope
main.cpp:7:24: error: 'shoppingCartInput' was not declared in this scope
main.cpp:7:43: error: 'string' was not declared in this scope
main.cpp:7:51: error: 'firstname' was not declared in this scope
main.cpp:7:62: error: 'string' was not declared in this scope
main.cpp:7:70: error: 'lastname' was not declared in this scope
main.cpp:102:50: error: 'getName' was not declared in this scope

代码如下:

#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>
#include <cctype>

void getName(ifstream& shoppingCartInput, string& firstname, string& lastname);

using namespace std;
int main()
{
    // declerations
    string infile_name = "";
    string shopper = "";
    string firstname ="";
    string lastname = "";
    int quantity;
    double price = 0.0, leastExpPrice = 0, mostExpPrice = 0;
    string item, leastExpItem, mostExpItem;
    double totalCost = 0.0;
    //1) Open Your File
    cout << "please enter the name of the input file:";
    cin >> infile_name;
    cout << "\n";
    ifstream shoppingCartInput;
    ofstream shoppingCartOutput;
    shoppingCartInput.open(infile_name.c_str());
    if(shoppingCartInput.fail( )) {
    cout << "Input file opening failed.\n";
    exit(1);
    }
    shoppingCartOutput.open("output_file.dat");
    if(shoppingCartOutput.fail( )) {
        cout << "Output file opening failed.\n";
        exit(1);
    }
    //2) Read the first line
    shoppingCartInput >> quantity >> price >> item;
    //printing the line to the console (properly organized)
    shoppingCartOutput.setf(ios::fixed);
    shoppingCartOutput.setf(ios::showpoint);
    shoppingCartOutput.setf(ios::left);
    shoppingCartOutput.width(15);
    shoppingCartOutput << item << " ";
    shoppingCartOutput.setf(ios::right);
    shoppingCartOutput.width(3);
    shoppingCartOutput << quantity << " ";
    shoppingCartOutput.setf(ios::right);
    shoppingCartOutput.width(6);
    shoppingCartOutput.precision(2);
    shoppingCartOutput << price << " ";
    shoppingCartOutput.setf(ios::right);
    shoppingCartOutput.width(7);
    shoppingCartOutput.precision(2);
    shoppingCartOutput << (quantity * price) << endl;
    //set it as the most expensive
    //set it as the least expensive
    leastExpPrice = price;
    leastExpItem = item;
    mostExpPrice = price;
    mostExpItem=item;
    //initialize total cost to get the cost of the first line of data
    totalCost = (quantity * price);
    //3) Read until the end of the file
    while(!(shoppingCartInput.eof())) {
        while(quantity != -1) {
            shoppingCartInput >> quantity >> price >> item;
            //printing the line to the console (properly organized)
            shoppingCartOutput.setf(ios::fixed);
            shoppingCartOutput.unsetf(ios::right);
            shoppingCartOutput.setf(ios::showpoint);
            shoppingCartOutput.setf(ios::left);
            shoppingCartOutput.width(15);
            shoppingCartOutput << item << " ";
            shoppingCartOutput.setf(ios::right);
            shoppingCartOutput.width(3);
            shoppingCartOutput << quantity << " ";
            shoppingCartOutput.setf(ios::right);
            shoppingCartOutput.width(6);
            shoppingCartOutput.precision(2);
            shoppingCartOutput << price << " ";
            shoppingCartOutput.setf(ios::right);
            shoppingCartOutput.width(7);
            shoppingCartOutput.precision(2);
            shoppingCartOutput << (quantity * price) << endl;
            if(price < leastExpPrice) {
                leastExpPrice = price;
                leastExpItem = item;
            }
            if(price > mostExpPrice) {
                mostExpPrice = price;
                mostExpItem=item;
            }
            totalCost += (quantity * price);
        }
        if (quantity == (-1)) {
            string first = "";
            string last = "";
            getName(shoppingCartInput, firstname, lastname);
            shopper = firstname + " " + lastname;
            shoppingCartOutput << "\ncheapest item = " << leastExpItem <<
                        endl;
            shoppingCartOutput << "most expensive item = " << mostExpIte <<
                        endl;
            shoppingCartOutput << "total cost = " << totalCost << endl;
            shoppingCartOutput.unsetf(ios::right);
            shoppingCartOutput.setf(ios::left);
            shoppingCartOutput << "shopper = " << shopper;
        }
    }
    shoppingCartInput.close();
    shoppingCartOutput.close();
    return 0;
}

void getName(ifstream& shoppingCartInput, std::string& firstname, std::string&
lastname)
{
    char letter;
    do {
         shoppingCartInput.get(letter);
         firstname += letter - 1;
    } while (letter != ',');

    do {
        shoppingCartInput.get(letter);
        lastname += letter;
    } while (letter != '\n' || letter != 'r');
}

Answer 1

对你来说，这就是 std::ifstream。或者，在所有 #includes 之后和其余代码之前添加 using namespace std;。