以下代码的目的是获取用户输入的6个电影标题和重新发布日期，使用fstream将该数据写入文件，然后在循环中将数据读入2个字符串字符（line1和line2），这样第一个循环将为第一个电影标题和年份分配第1行和第2个第二个循环，第二个循环将为第1个电影标题和年份分配第1和第2个电影，依此类推，直到eof。
// array of structures
#include <iostream>
#include <string>
#include <sstream>
#include <istream>
#include <stdio.h>
#include <cctype>
#include <fstream>
#include <cassert>
#include <assert.h>
using namespace std;
#define NUM_MOVIES 6
struct movies_iit
{
string title;
int year;
}
films[NUM_MOVIES];
// global variables
char title[20], y, n;
int year;
string search;
// function 1
void sort_on_title(movies_iit films[], int n)
{
// Local struct variable used to swap records
movies_iit temp;
for (int i = 0; i < n - 1; i++)
{
for (int i = 0; i < n - 1; i++)
{
/* If s[i].title is later in alphabet than
s[i+1].title, swap the two records */
if (films[i].title > films[i + 1].title)
{
temp = films[i];
films[i] = films[i + 1];
films[i + 1] = temp;
}
}
}
}
//end function 1
//function query1 prototype
void query1(movies_iit movie);
// function query2 prototype
void query2(movies_iit movie);
// function 2 prototype
void printmovie(movies_iit movie);
int main()
{
// login
// username: user
// password: word
string mystr, pass, name, line1, line2;
int n;
char response;
// output object
ofstream fout("data.dat");
// input object
ifstream fin("data.dat");
assert(fin.is_open());
cout << "enter your username " << endl;
cin >> name;
cout << "enter your password " << endl;
cin >> pass;
cout << "\n" << endl;
if (name == "user" && pass == "word")
cout << "Welcome, user." << endl;
else
{
cout << "###" << "unrecognized username/password combination" << "\t" << "please try again" << "###" << endl;
system("PAUSE");
return 0;
}
cin.ignore(std::numeric_limits < std::streamsize > ::max(), '\n');
cout << "\n" << endl;
for (n = 0; n < NUM_MOVIES; n++)
{
cout << "Enter title: ";
getline(cin, films[n].title);
cout << "Enter year: ";
getline(cin, mystr);
stringstream(mystr) >> films[n].year;
}
cout << "\n" << endl;
for (int i = 0; i < NUM_MOVIES; ++i)
{
fout << films[i].title << "\n";
fout << films[i].year << "\n";
}
// sort records, function 1 call
sort_on_title(films, NUM_MOVIES);
cout << "\nYou have entered these movies:\n";
for (n = 0; n < NUM_MOVIES; n++)
printmovie(films[n]); // function 2 call
cout << "Perform an alphabetical search? (y/n)" << endl;
cin >> response;
if (response == 'y')
{
cout << "Please enter title" << endl;
cin >> title;
if (fin)
{
getline(fin, line1); // read first 2 recs
getline(fin, line2);
while (fin) // keep reading till the eof
{
if (line1 == "title")
{
cout << " >> " << line1 << endl;
cout << line2 << endl;
}
else
{
cout << line1 << endl;
cout << line2 << endl;
}
}
}
fin.close(); //close input file
response == n;
}
else if (response == 'n')
cout << "\n" << endl;
else
cout << "invalid entry" << endl;
cout << "\n" << endl;
}
// function 2 definition
void printmovie(movies_iit movie)
{
cout << movie.title;
cout << " (" << movie.year << ")\n";
}
// function query1 defintion
void query1(movies_iit movie)
{
if (movie.title == "title")
{
cout << " >> " << movie.title;
cout << " (" << movie.year << ")\n";
}
else
{
cout << movie.title;
cout << " (" << movie.year << ")\n";
}
}
// function query2 definition
void query2(movies_iit movie)
{
if (movie.year >= year)
{
cout << movie.title;
cout << " (" << movie.year << ")\n";
}
}
在我从文件中读取值到我的字符串的循环中，在我的输出中它不显示存储在字符串中的数据。为什么会这样，我该如何解决这个问题？
我意识到我最初发布的代码不起作用;这是一个功能性的。
答案 0 :(得分：1)
你需要关闭＆＃39; fout＆＃39;在您尝试使用＆＃39; fin＆＃39;来尝试阅读之前的文件流。
fout.close（）; //＆lt; ==关闭输出文件以刷新缓冲的I / O
您写入文件的数据可能已缓冲（不立即写入文件）。当您尝试在搜索过程中阅读时，您的data.dat文件为空。
答案 1 :(得分：1)
getline（）应该在while循环中（因为你想匹配所有的行，而不仅仅是前2个记录）
int main (){
//login
//username: user
//password: word
string mystr, pass, name, line1, line2;
int n;
char response;
//output object
ofstream fout ("data.dat");
//input object
cout << "enter your username "<<endl;
cin >> name;
cout << "enter your password "<<endl;
cin >> pass;
cout << "\n" << endl;
if (name == "user" && pass == "word")
cout << "Welcome, user." << endl;
else
{cout << "###" << "unrecognized username/password combination" << "\t" << "please try again" << "###" << endl;
//system("PAUSE");
return 0;
}
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
cout << "\n" << endl;
for (n=0; n<NUM_MOVIES; n++)
{
cout << "Enter title: ";
getline (cin,films[n].title);
cout << "Enter year: ";
getline (cin,mystr);
stringstream(mystr) >> films[n].year;
}
cout << "\n" << endl;
//###################################################################################################################
//write to file
//###################################################################################################################
for (int i = 0; i < NUM_MOVIES; ++i)
{
fout << films[i].title << "\n";
fout << films[i].year << "\n";
}
fout.close();
//sort records, function 1 call
sort_on_title(films, NUM_MOVIES);
cout << "\nYou have entered these movies:\n";
for (n=0; n<NUM_MOVIES; n++)
printmovie (films[n]); //function 2 call
ifstream fin("data.dat");
assert(fin.is_open());
//###################################################################################################################
//query 1
//###################################################################################################################
cout << "Perform an alphabetical search? (y/n)" << endl;
cin >> response;
if (response == 'y')
{cout << "Please enter title" << endl;
cin >> title;
if (fin.good())
{
while(!fin.eof()) //keep reading till the eof
{
getline(fin,line1); // read first 2 recs
if(!fin.eof())
getline(fin,line2);
if (line1 == title)
{
cout << " >> " << line1 << endl;
cout << line2 << endl;
}
// else
// {
// cout << line1 << endl;
// cout << line2 << endl;
// }
}
}
fin.close(); //close input file
response == n;
}
else if (response == 'n')
cout << "\n" << endl;
else
cout << "invalid entry" << endl;
cout << "\n" << endl;
}