Assigning variables information from a infile txt C++ - c++

Question

This is my text file:
12345 shoe 5 0
34534 foot 72 1
34562 race 10 0
34672 chicken 24 150
88 pop 65 0
I need to take this file and go row by row, assign the first number as an identifier itemNum, second word as itemName, third number as itemPrice, and last number as itemAdjusmentValue. I will need to perform arithmetic with the last two numbers itemPrice and itemAdjusmentValue.
Code so far:
using namespace std;
// making a struct to store each value of the cuadre
struct Cuadre
{
int itemNum;
string itemName;
int itemPrice;
int itemAdjusment;
};
int main (){
ifstream infile("sheet_1.txt");
string checkLine;
if (infile.is_open()){
while ( infile.good()){
getline (infile, checkLine);
cout << checkLine << endl;
}
}
else
cout << "error with name of file" << endl;
vector<Cuadre> procedures;
Cuadre line;
while(Cuadre >> line.itemNum >> line.itemName >> line.itemPrice >> line.itemAdjusment){
procedures.push_back(line);
}
This code generates an error on the last while statement
expected primary-expression before '>>' token
I cant really find a specific tutorial on how to do this, and i've looked a good amount.

Answer 1

From the code you posted, (with reference to the >> istream operators) it looks like you want to stream the contents of the string data read from your file into the members of a struct.
It is not possible to stream directly from a std::string (eg: checkLine >> x >> y >> z), as string does not provide a streaming interface.
In order to do that you need to use a stream, such as std::stringstream.
You could populate a with your string checkLine, and then stream from that into your data members
std::stringstream ss(checkLine);
ss >> line.itemNum >> line.itemName >> line.itemPrice >> line.itemAdjusment;
Example code:
#include <iostream>
#include <fstream>
#include <vector>
#include <sstream>
using namespace std;
// making a struct to store each value of the cuadre
struct Cuadre
{
int itemNum;
string itemName;
int itemPrice;
int itemAdjusment;
};
int main (){
ifstream infile("sheet_1.txt");
string checkLine;
vector<Cuadre> procedures;
if (infile.is_open()){
while ( infile.good()){
getline (infile, checkLine);
cout << checkLine << endl;
Cuadre line;
std::stringstream ss(checkLine);
ss >> line.itemNum >> line.itemName >> line.itemPrice >> line.itemAdjusment;
procedures.push_back(line);
}
}
else
cout << "error with name of file" << endl;
return 0;
}

Answer 2

You need to push into the vector inside the loop that reads from the file. And you should be getting the fields from checkLine -- Cuadre is a type name, not a variable you can read from. But to do that you need to create a stringstream.
int main (){
ifstream infile("sheet_1.txt");
string checkLine;
vector<Cuadre> procedures;
if (infile.is_open()){
while (getline (infile, checkLine)){
Cuadre line;
cout << checkLine << endl;
stringstream linestream(checkline);
if (linestream >> line.itemNum >> line.itemName >> line.itemPrice >> line.itemAdjusment) {
procedures.push_back(line);
} else {
cout << "incorrect line" << endl;
break;
}
}
}
else {
cout << "error with name of file" << endl;
}
}
while (infile.good()) is also not correct, it's essentially the same as while (!infile.eof()). See Why is iostream::eof inside a loop condition considered wrong?

Answer 3

You can try reading directly into struct as well:
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
struct Cuadre
{
int itemNum;
std::string itemName;
int itemPrice;
int itemAdjusment;
};
int main()
{
std::vector<Cuadre> procedures;
std::ifstream infile("sheet_1.txt");
while (infile)
{
Cuadre line;
if (infile >> line.itemNum >> line.itemName >> line.itemPrice >> line.itemAdjusment)
procedures.push_back(line);
else
break;
}
if (!procedures.empty())
{
for (auto &p : procedures)
std::cout
<< "itemNum: " << p.itemNum << "\t"
<< "itemName: " << p.itemName << "\t"
<< "itemPrice: " << p.itemPrice << "\t"
<< "itemAdjusment: " << p.itemAdjusment
<< std::endl;
}
else
std::cout << "error with file or data" << std::endl;
return 0;
}
Prints:
itemNum: 12345 itemName: shoe itemPrice: 5 itemAdjusment: 0
itemNum: 34534 itemName: foot itemPrice: 72 itemAdjusment: 1
itemNum: 34562 itemName: race itemPrice: 10 itemAdjusment: 0
itemNum: 34672 itemName: chicken itemPrice: 24 itemAdjusment: 150
itemNum: 88 itemName: pop itemPrice: 65 itemAdjusment: 0

Answer 4

If you define an overload of >> for your type Cuadre, you can read directly from the file into Cuadre objects.
std::istream& operator>>(std::istream& is, Cuadre & cuadre)
{
std::string s;
getline(is, s);
std::cout << s;
std::stringstream ss(s);
ss >> cuadre.itemNum >> cuadre.itemName >> cuadre.itemPrice >> cuadre.itemAdjusment;
return is;
// or without logging
return is >> cuadre.itemNum >> cuadre.itemName >> cuadre.itemPrice >> cuadre.itemAdjusment;
}
int main (){
ifstream infile("sheet_1.txt");
vector<Cuadre> procedures;
for (Cuadre line; infile >> line;) {
procedures.push_back(line);
}
// or with #include <algorithm>
std::copy(std::istream_iterator<Cuadre>{ infile }, {}, std::back_inserter(procedures));
}