Question

所以我正在学习如何输出到文件，但插入运算符“＆lt;＆lt;”没有得到承认。

所以每次我在下面的代码中使用“OutFile＆lt;＆lt;”时，visual studio会标记“＆lt;＆lt;＆lt;”无效。

我想也许这是我的包含语句的问题，但我仔细检查过，对我来说似乎并非如此。

完整错误

"1>z:\cst 113 - programming\purdyjex4\purdyjex4.cpp(111): error C2784: 'std::basic_ostream<_Elem,_Traits> &std::operator <<(std::basic_ostream<_Elem,_Traits> &,const std::basic_string<_Elem,_Traits,_Alloc> &)': could not deduce template argument for 'std::basic_ostream<_Elem,_Traits> &' from 'std::ifstream'
1>  c:\program files (x86)\microsoft visual studio 14.0\vc\include\string(167): note: see declaration of 'std::operator <<'"

我的代码：

//Include - to use input & output on the screen
#include <iostream>

//Include - For file output and input
#include <fstream>

//Include - to use input and Output Manipulators
#include <iomanip>

//Include - to use string variables
#include <string>

//namespace using statement must be included to use the standard header files
using namespace std;

//Constant for programmer's name
const string MY_NAME = "Justin T Purdy";

//Constant for Course & Exercise Number
const string COURSE = "CST 113 - Exercise 4";

//To make outputting headers easier, store character and width for deviders
const int SCREEN_WIDTH = 79;
const char SYMBOL = '*';

//Cost Ratios
const double DAY_COST = 0.1;
const double NIGHT_COST = 0.25;

//Name of files user can open
const string FILE_NAMES[2] = { "Ex4-1.txt","Ex4-2.txt" };


int main(void)
{
    //Declare variables; Step 1
    ifstream inFile;
    ifstream outFile;

    //Create variables to be used
    //I'm using arrays for some variables
    string customerFirstName[3];
    string customerLastName[3];
    string customerFullName[3];
    int fileNumber;
    int dayMinutes[3];
    int nightMinutes[3];
    double totalCosts[3] = { 0 };
    double grandTotal = 0;

    //Output deviders
    cout << setfill(SYMBOL) << setw(SCREEN_WIDTH) << SYMBOL << setfill(' ')
        << endl;

    //Get file number from user
    cout << "Select from these two file names: " << endl
        << "        1: Ex4-1.txt" << endl << "      2: Ex4-2.txt" << endl;
    cout << setfill(SYMBOL) << setw(SCREEN_WIDTH) << SYMBOL << setfill(' ')
        << endl;
    cout << "Enter the number of the input file: ";
    cin >> fileNumber;

    //Check if invalid number, terminate program if number invalid
    if (fileNumber > 2)
    {
        cout << endl << "You have entered a invalid fileNumber and the program terminated.";
        return 0;
    }

    //Open file the user specified
    inFile.open(FILE_NAMES[fileNumber]);
    outFile.open("Ex4-Out.txt");

    //Get data from opened file, put it into variables
    inFile >> customerFirstName[1] >> customerLastName[1] >> dayMinutes[1] >> nightMinutes[1]
        >> customerFirstName[2] >> customerLastName[2] >> dayMinutes[2] >> nightMinutes[2]
        >> customerFirstName[3] >> customerLastName[3] >> dayMinutes[3] >> nightMinutes[3];


    //Calculation total costs using data from file
    totalCosts[1] = (dayMinutes[1] * DAY_COST) + (nightMinutes[1] * NIGHT_COST);
    totalCosts[2] = (dayMinutes[2] * DAY_COST) + (nightMinutes[2] * NIGHT_COST);
    totalCosts[3] = (dayMinutes[3] * DAY_COST) + (nightMinutes[3] * NIGHT_COST);
    grandTotal = totalCosts[1] + totalCosts[2] + totalCosts[3];


    //Output header into output file
    outFile << setfill(SYMBOL) << setw(SCREEN_WIDTH) << SYMBOL << setfill(' ')
        << endl << MY_NAME << endl << COURSE << "CELL PHONE BILL"
        << setfill(SYMBOL) << setw(SCREEN_WIDTH) << SYMBOL << setfill(' ');

    //Output name of columns to output file
    outFile << right << setw(10) << "Phone" << setw(20) << "Name"
        << setw(15) << "Day" << setw(15) << "Night" << setw(15)
        << "Total" << endl << setw(45) << "Minutes" << setw(15)
        << "Minutes" << setw(15) << "Cost" << setfill(SYMBOL) <<
        setw(SCREEN_WIDTH) << SYMBOL << setfill(' ');

    //Output first row of data
    outFile << right << setw(10) << "1" << setw(20) << customerFirstName[1]
        << setw(15) << dayMinutes[1] << setw(15) << nightMinutes[1] << setw(15)
        << totalCosts[1] << endl;

    //Output second row of data
    outFile << right << setw(10) << "2" << setw(20) << customerFirstName[2]
        << setw(15) << dayMinutes[2] << setw(15) << nightMinutes[2] << setw(15)
        << totalCosts[2] << endl;

    //Output third row of data
    outFile << right << setw(10) << "3" << setw(20) << customerFirstName[3]
        << setw(15) << dayMinutes[3] << setw(15) << nightMinutes[3] << setw(15)
        << totalCosts[3] << endl;

    //Output grand total
    outFile << setfill(SYMBOL) << setw(SCREEN_WIDTH) << SYMBOL << setfill(' ')
        << left << "Total family cost:" << right << grandTotal;

    //Close file
    inFile.close();
    outFile.close();

    return 0;
}

Answer 1

此ifstream outFile;应为ofstream outFile;。否则你将写入一个输入文件而且没有定义。

C ++ - 错误C2784： - 参见'std :: operator＆lt;＆lt;'的声明

1 个答案: