C ++。 如何从文件读取并与输入匹配

Question

I am trying to read a textfile and matching the fruit to what I have type(eg I type apple and it will search the textfile for the word apple and match it and output that it's been found) but I am struggling to achieve the results I wanted and thus need help in it.

I have a text file (fruit.txt) with contents shown below

apple,30

banana,20

pear,10

---

this is my code

string fruit;
string amount;
string line = " ";
ifstream readFile("fruit.txt");
fstream fin;

cout << "Enter A fruit: ";
cin >> fruit;

fin >> fruit >> amount;
while (getline(readFile, line,','))
    {
        if(fruit != line) {
            cout <<"the fruit that you type is not found.";
        }

       else {
           cout <<"fruit found! "<< fruit;
       }
}

please advise thanks.

Answer 1

In the loop with getline you read "apple" into line the first loop, and "30\\nbanana" into line the second time, etc.

Instead read the whole line (using getline ), and then use eg std::istringstream to extract the fruit and amount.

Something like:

std::string line;
while (std:::getline(readFile, line))
{
    std::istringstream iss(line);

    std::string fruit;
    if (std::getline(iss, fruit, ','))
    {
        // Have a fruit, get amount
        int amount;
        if (iss >> amount)
        {
            // Have both fruit and amount
        }
    }
}

Answer 2

I will start by saying that I am just a beginner like you, took your code and made some changes, for example:

1. Used "fstream" to read from file until is not the end of the file.

2. Then reading each line into a stringstream so I can brake it later using the coma delimiter.

3. I've also used a two dimension array to store the fruits and the amount of each type.

4. In the end I had to search through the array for the fruit I wanted to display.

Before I post the code I want to warn you that the program wont work if there are more then 20 fruits with more than one property (in this case the amount). Here's the code:

#include <sstream>
#include <fstream>
#include <iostream>
#include <stdio.h>
using namespace std;

void main  (void)
{
    fstream readFile("fruit.txt");
    string fruit,amount,line;
    bool found = false;
    string fruitArray[20][2];

    cout << "Enter A fruit: ";
    cin >> fruit;

    while (!readFile.eof())
    {
        int y =0 ;
        int x =0 ;
        getline(readFile,line);
        stringstream ss(line);
        string tempFruit;
        while (getline(ss,tempFruit,','))
        {
            fruitArray[x][y] = tempFruit;
            y++;
        }
        x++;
    }

    for (int i = 0; i < 20; i++)
    {
        for (int ii = 0; ii < 2; ii++)
        {
            string test = fruitArray[i][ii] ;
            if  (test == fruit)
            { 
                amount = fruitArray[i][ii+1];
                found = true;
                break;
            } 
            else{
                cout <<"Searching" << '\n';
            } 
        }
        if (found){
            cout << "Found: " << fruit << ". Amount:" << amount << endl;
            break;
        }
    }
    cout << "Press any key to exit he program.";
    getchar();
}

Hope you've learned something from it ( I sure did).