How to print specific array entries from a .txt file in C++? - c++

Question

First, I'm very new to coding in C++.
So, I have a .txt file, with names and numbers--here's an example.
chris 5
tara 7
Sam 13
Joey 15
I would like to use this code to retrieve the names and numbers, but how does one print specific array entries instead of just the variables name and number (I want it to show the name and the number on the screen)?
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main() {
string name;
int number;
struct sEntry
{
std::string name;
int number;
};
sEntry entries[256];
std::ifstream fin("input.txt"); // opens the text file
int nb_entries; // Keeps track of the number of entries read.
for (nb_entries = 0; fin.good() && nb_entries < 256; nb_entries++) // Keep going until we hit the end of the file:
{
fin >> entries[nb_entries].name;
fin >> entries[nb_entries].number;
cout << "Here, "<< name <<" is name.\n";
cout << "Here, "<< number <<" is number.\n";
}
}

Answer 1

You're writing out name and number, but those aren't the variables you've read. You've read array entries.
Getting it working as simply as possible just comes down to changing your cout lines to be:
cout << "Here, " << entries[nb_entries].name << " is name.\n";
cout << "Here, " << entries[nb_entries].number << " is number.\n";
No need for a std::vector, ther's nothing wrong with how you've done it.

Answer 2

Instead of using a plain C array of sEntry you should use a C++ vector instead (which can change size dynamically). Then you create a new sEntry instance inside your loop (which can just use fin.eof() as termination condition then) and use the operator>>() to assign the values. Afterwards you use push_back() to add the sEntry instances to your vector.
You need to use the sEntry.name, sEntry.number fields for output on the screen, name and number as shown in your code won't ever receive values.
#include <vector>
#include <string>
#include <iostream>
struct sEntry
{
std::string name;
int number;
};
int main() {
string name;
int number;
std::vector<sEntry> entries;
std::ifstream fin("input.txt"); // opens the text file
// int nb_entries; // Keeps track of the number of entries read. -> not necessary, use entries.size()
while(!fin.eof()) // Keep going until we hit the end of the file:
{
sEntry entry;
fin >> entry.name;
fin >> entry.number;
cout << "Here, "<< entry.name <<" is name.\n";
cout << "Here, "<< entry.number <<" is number.\n";
entries.push_back(entry);
}
}