将带有结构的向量序列化为 .dat 文件，我做错了什么？

Question

如果我输入

描述：苹果

数量：10

批发成本：30

零售成本：20

添加日期：12 月

这些是我的 .dat 文件中的内容：

1Apple103020十二月

但是当我加载我的程序时，它没有正确加载结构，导致我的列表中有 0 个项目。这是它应该看起来的样子还是我做错了什么。

代码：

#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
#include <vector>

using namespace System;
using namespace std;
#pragma hdrstop

bool isValidChoice(int size, int choice);

template<typename T>
void writeVector(ofstream &out, const vector<T> &vec);

template<typename T>
vector<T> readVector(ifstream &in);

template<typename T>
vector<T> addItem(vector<T> &vec);

template<typename T>
void printItemDescriptions(vector<T> &vec);

template<typename T>
int displayRecord(vector<T> &vec);

struct InventoryItem {
    string Description;
    int Quantity;
    int wholesaleCost;
    int retailCost;
    string dateAdded;
} ;


int main(void)
{
    cout << "Welcome to the Inventory Manager extreme! [Version 1.0]" << endl;
    ifstream in("data.dat");
    if (in.is_open()) { cout << "File \'data.dat\' has been opened successfully." << endl; } else { cout << "Error opening data.dat" << endl;}
    cout << "Loading data..." << endl;
    vector<InventoryItem> structList = readVector<InventoryItem>( in );
    cout <<"Load complete." << endl << endl;
    in.close();


    while (1)
    {

        string line = "";
        cout << "There are currently " << structList.size() << " items in memory.";
        cout << endl << endl;
        cout << "Commands: " << endl;
        cout << "1: Add a new record " << endl;
        cout << "2: Display a record " << endl;
        cout << "3: Edit a current record " << endl;
        cout << "4: Delete a record " << endl;
        cout << "5: Save current information " << endl;
        cout << "6: Exit the program " << endl;
        cout << endl;
        cout << "Enter a command 1-6: ";

        getline(cin , line);

        int rValue = atoi(line.c_str());

        system("cls");

        ofstream out("data.dat");

        switch (rValue)
        {
            case 1:
                addItem(structList);
                break;
            case 2:
                displayRecord(structList);
                break;
            case 3:
                break;
            case 4:
                break;
            case 5:
                if (!structList.size()) { cout << "There are no items to save! Enter one first!" << endl << endl; system("pause"); system("cls"); break; }
                writeVector(out , structList);
                break;
            case 6:
                return 0;
            default:
                cout << "Command invalid. You can only enter a command number 1 - 6. Try again. " << endl;
        }

        out.close();
    }

    system("pause");

    return 0;
}

template<typename T>
void writeVector(ofstream &out, const vector<T> &vec)
{
    out << vec.size();

    for(vector<T>::const_iterator i = vec.begin(); i != vec.end(); i++)
    {
        out << *i;
    }
    cout << "Save completed!" << endl << endl;
}

ostream &operator<<(ostream &out, const InventoryItem &i)
{
    out << i.Description;
    out << i.Quantity;
    out << i.wholesaleCost << i.retailCost;
    out << i.dateAdded;
    return out;
}

istream &operator>>(istream &in, InventoryItem &i)
{
    in >> i.Description;
    in >> i.Quantity;
    in >> i.wholesaleCost >> i.retailCost;
    in >> i.dateAdded;
    return in;
}



template<typename T>
vector<T> readVector(ifstream &in)
{
    size_t size;
    if (in.fail())
    {
    in >> size;
    } else {
        size = 0;
    }

    vector<T> vec;
    vec.reserve(size);

    for(unsigned int i = 0; i < size; i++)
    {
        T tmp;
        in >> tmp;
        vec.push_back(tmp);
    }

    return vec;
}

template<typename T>
vector<T> addItem(vector<T> &vec)
{
    system("cls");

    string word;
    unsigned int number;

    InventoryItem newItem;

    cout << "-Add a new item-" << endl << endl;
    cout << "Enter the description for the item: ";
    getline (cin , word);
    newItem.Description = word;

    cout << endl;
    cout << "Enter the quantity on hand for the item: ";
    getline (cin , word);
    number = atoi(word.c_str());
    newItem.Quantity = number;

    cout << endl;
    cout << "Enter the Retail Cost for the item: ";
    getline (cin , word);
    number = atoi(word.c_str());
    newItem.retailCost = number;

    cout << endl;
    cout << "Enter the Wholesale Cost for the item: ";
    getline (cin , word);
    number = atoi(word.c_str());
    newItem.wholesaleCost = number;

    cout << endl;
    cout << "Enter current date: ";
    getline (cin , word);
    newItem.dateAdded = word;

    vec.push_back(newItem);

    return vec;
}

template<typename T>
void printItemDescriptions(vector<T> &vec)
{
    int size = vec.size();

    if (size)
    {
        cout << "---------------------------------" << endl;
        cout << "|      ~ Item Descriptions ~    |" << endl;
        cout << "---------------------------------" << endl;
        cout << "*********************************" << endl;
        for (int i = 0 ; i < size ; i++)
        {
            cout << "(" << i+1 << ")" << ": " << vec[i].Description << endl;
        }
        cout << "*********************************" << endl << endl;
    }
}

template<typename T>
int displayRecord(vector<T> &vec)
{
    string word = "";
    string quit = "quit";
    int choice = 1;
    int size = vec.size();

    if (size)
    {
        printItemDescriptions(vec);
        cout << endl;

        while (1)
        {
            cout << "Type \"exit\" to return to the Main Menu." << endl << endl;
            cout << "Enter \"list\" to re-display the items." << endl << endl;
            cout << endl;
            cout << "Pick the number of the item you would like to display: ";
            getline (cin , word);

            if (convertToLower(word) == "exit") { system("cls"); return 0; }
            if (convertToLower(word) == "list") { system("cls"); displayRecord(vec); }

            choice = atoi(word.c_str());

            if (isValidChoice(size, choice))
            {
                system("cls");
                cout << endl << "[Item (" << choice << ") details] " << endl << endl;
                cout << "******************" << endl;
                cout << "*  Description   * " << vec[choice-1].Description << endl;
                cout << "******************" << endl << endl;
                cout << "******************" << endl;
                cout << "*Quantity On Hand* " << vec[choice-1].Quantity << endl;
                cout << "******************" << endl << endl;
                cout << "******************" << endl;
                cout << "* Wholesale Cost * " << vec[choice-1].wholesaleCost << endl;
                cout << "****************** " << endl << endl;
                cout << "******************" << endl;
                cout << "*  Retail Cost   * " << vec[choice-1].retailCost << endl;
                cout << "****************** " << endl << endl;
                cout << "******************" << endl;
                cout << "*  Data Added    * " << vec[choice-1].dateAdded << endl;
                cout << "****************** " << endl << endl;
            } else { system("cls"); cout << "That item doesn't exist!" << endl; cout << "Pick another item or enter \"list\" to see available items." << endl << endl; }
        }
    } else { cout << "There are currently no items to display." << endl << endl; system("pause"); system("cls"); return 0; }

    return 1;
}

bool isValidChoice(int size, int choice)
{
    for (int i = 0 ; i <= size ; i++)
    {
        if (choice == size) { return true; }
    }
    return false;
}

string convertToLower(string word)
{
    for (unsigned int i = 0 ; i < word.size() ; i++)
    {
        word[i] = tolower(word[i]);
    }

    return word;
}

Answer 1

在您的阅读功能中：

   if (in.fail())

应该是：

   if ( ! in.fail())

或者更好：

int n;

if ( ! (in >> n) ) {
  n = 0;
}

Answer 2

为结构项目使用一些分隔符，例如" "（空格）

Answer 3

同样，序列化是一项不那么简单的任务。如果您可以花时间学习图书馆。

我不会重新发布我给你上一个问题的answer，但我相信你真的应该看看它。它解释了您面临的一些问题并提供了解决方案。

Answer 4

保存 DAT 文件时，您需要在字符串之间添加一个空格（空格/制表符）。

使用 operator>> 读取字符串时，它会读取一个字符串，直到找到第一个空白字符（空格/制表符/EOL）。

来自您的代码：

ostream &operator<<(ostream &out, const InventoryItem &i)
{
    out << i.Description << ' ';
    out << i.Quantity << ' ';
    out << i.wholesaleCost  << ' ' << i.retailCost  << ' ';
    out << i.dateAdded  << ' ';
    return out;
}

更新

即便如此，当使用 operator>> 加载描述时，例如，描述将不完整（加载到保存的描述文本中的第一个空格）。