每次我做任何事情，而我的while（1）在我的主函数中被调用，我的文件被清除。这让我疯狂。我已经尝试过一切了。我试着把我的ofstream输出（“data.dat”）;在while（1）语句之外所以它不是每次调用，但是没有任何内容写入文件，就像ofstream甚至没有工作一样！
我试图将ofstream设为静态，因此不会像以下那样一遍又一遍地调用：
static ofstream open("data.dat");
这不起作用。
就像我说的那样，当我把whilestream OUTSIDE放入while语句时，没有任何内容写入文件。像：
ofstream out("data.dat");
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");
switch (rValue)
{
case 1:
structList = addItem(structList);
break;
case 2:
displayRecord(structList);
break;
case 3:
structList = editRecord(structList);
break;
case 4:
deleteRecord(structList);
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();
}
有人可以告诉我为什么我的检查以防止读取空文件不起作用？
我的支票：
bool checkFileEmpty()
{
ifstream in("data.dat");
if (in.peek() == in.eofbit)
{
return true;
}
return false;
}
我厌倦了我的程序在启动时一遍又一遍地崩溃，因为我的矢量设置为2亿的大小。我为此尝试了一些东西...没有一个有效......请上帝帮助我这两个！我已经工作了18个小时（整晚都是），我几乎已经完成了。我求求你......
我的代码：
#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);
bool checkFileEmpty();
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);
template<typename T>
vector<T> editRecord(vector<T> &vec);
template<typename T>
vector<T> deleteRecord(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:
structList = addItem(structList);
break;
case 2:
displayRecord(structList);
break;
case 3:
structList = editRecord(structList);
break;
case 4:
deleteRecord(structList);
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 (checkFileEmpty())
{
size = 0;
} else {
in >> size;
}
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());
choice -= 1;
if (isValidChoice(size, choice))
{
system("cls");
cout << endl << "[Item (" << choice << ") details] " << endl << endl;
cout << "******************" << endl;
cout << "* Description * " << vec[choice].Description << endl;
cout << "******************" << endl << endl;
cout << "******************" << endl;
cout << "*Quantity On Hand* " << vec[choice].Quantity << endl;
cout << "******************" << endl << endl;
cout << "******************" << endl;
cout << "* Wholesale Cost * " << vec[choice].wholesaleCost << endl;
cout << "****************** " << endl << endl;
cout << "******************" << endl;
cout << "* Retail Cost * " << vec[choice].retailCost << endl;
cout << "****************** " << endl << endl;
cout << "******************" << endl;
cout << "* Data Added * " << vec[choice].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 == i) { return true; }
}
return false;
}
string convertToLower(string word)
{
for (unsigned int i = 0 ; i < word.size() ; i++)
{
word[i] = tolower(word[i]);
}
return word;
}
bool checkFileEmpty()
{
ifstream in("data.dat");
if (in.peek() == in.eofbit)
{
return true;
}
return false;
}
template<typename T>
vector<T> editRecord(vector<T> &vec)
{
string word;
int choice;
printItemDescriptions(vec);
cout << "Choose item to edit: ";
getline ( cin, word );
choice = atoi(word.c_str());
system("cls");
unsigned int number;
InventoryItem newItem;
cout << "-Edit an item-" << endl << endl;
cout << "Enter the description for the item: ";
getline (cin , word);
vec[choice-1].Description = word;
cout << endl;
cout << "Enter the quantity on hand for the item: ";
getline (cin , word);
number = atoi(word.c_str());
vec[choice-1].Quantity = number;
cout << endl;
cout << "Enter the Retail Cost for the item: ";
getline (cin , word);
number = atoi(word.c_str());
vec[choice-1].retailCost = number;
cout << endl;
cout << "Enter the Wholesale Cost for the item: ";
getline (cin , word);
number = atoi(word.c_str());
vec[choice-1].wholesaleCost = number;
cout << endl;
cout << "Enter current date: ";
getline (cin , word);
vec[choice-1].dateAdded = word;
system("cls");
cout << "Item edited successfully! " << endl;
return vec;
}
template<typename T>
vector<T> deleteRecord(vector<T> &vec)
{
if (!vec.size()) { cout << "There are no items to delete!" << endl << endl; return vec; }
printItemDescriptions(vec);
string word;
int choice;
cout << "Choose item to delete: ";
getline( cin, word);
choice = atoi(word.c_str());
vec.erase (vec.begin()+choice-1);
return vec;
}
答案 0 :(得分：2)
你最好在案例5中移动ofstream开启和关闭。
在这里，您可以在每次迭代时创建一个新文件。
case 5:
{
ofstream out("data.dat");
writeVector(out , structList);
out.close();
}
break;
答案 1 :(得分：0)
ofstream out("data.dat");
打开文件进行写入。默认情况下，它会从一开始就消除之前的任何内容。首先，使用与您正在读取的文件不同的输出文件。
答案 2 :(得分：0)
尝试添加接近案例6的陈述：
case 6:
out.close();
return 0;
我很确定关闭不会被调用，因为返回将在到达该语句之前退出main。如果文件未关闭，则会留下未刷新的缓冲区，我怀疑这会使数据不成文。
你应该在while循环之前将open打开，同时从while循环中删除out.close（），因为它将在第一个菜单选择后关闭文件。
答案 3 :(得分：0)
检查文件是否为空或无法打开
bool IsEmpty( const std::string & filename ) {
std::ifstream ifs( filename.c_str() );
if ( ifs.is_open() ) {
std::string line;
return ! std::getline( ifs, line );
}
else {
return true;
}
}