Using the getline function in C++ to extract certain characters - c++

Question

I need to get only specific characters from a text file. I am using the getline() function in C++. my compiler keeps giving me the error that there is no matching member function call for getline(), how can I fix that?
I'm trying to pull last names and scores from the file.
the file looks like:
Weems 50 60
Dale 51 60
Richards 57 60
...
Here's the code I'm trying:
#include <iostream>
#include <cmath>
#include <fstream>
using namespace std;
int main ()
{
//input variables
float GradeScore;
float TotalPoints;
float GradePercent;
string LastName;
ifstream myFile;
//open file
myFile.open ("/Users/ravenlawrence/Documents/TestGrades.rtf",ios::in);
// if file is open
if (myFile.is_open()) {
while(!myFile.eof()) {
string data;
getline(myFile,data); //reading data on line
myFile.getline(LastName, ' ');//storing data in LastName
myFile.getLine(GradeScore,' ');//storing data in GradeScore
myFile.getLine(TotalPoints,' ');//storing data in Total Points
cout << LastName << endl;
// cout<<data<<endl; //print it out
}
}
return 0;
}

Answer 1

Begin with a design, breaking down the work into small steps:
open file
loop, reading line from file while more lines
split line into fields
convert fields into variables
display variables
Now tackle each step
// open file
ifstream myFile ("/Users/ravenlawrence/Documents/TestGrades.rtf",ios::in);
if( ! myFile ) {
cerr << "cannot open file\n";
exit(1);
}
//loop, reading line from file while more lines
string data;
while( getline( myFile, data ) ) {
// split line into fields
std::stringstream sst(data);
std::string a;
std::vector<string> vfield;
while( getline( sst, a, ' ' ) )
vfield.push_back(a);
// ignore lines that do not contain exactly three fields
if( vfield.size() != 3 )
continue;
//convert fields into variables
LastName = vfield[0];
GradeScore = atof( vfield[1].c_str() );
TotalPoints = atof( vfield[2].c_str() );
// display
...
}

Answer 2

You do not need to use the function getline here, you can read file word by word.Secondly, you need to close the file after it reaches eof. Here is the code:
int main()
{
//input variables
float GradeScore;
float TotalPoints;
float GradePercent;
string LastName;
ifstream myFile;
//open file
myFile.open("check.txt", ios::in);
// if file is open
if (myFile.is_open()) {
while (!myFile.eof()) {
myFile >> LastName;//storing data in LastName
myFile >> GradeScore;//storing data in GradeScore
myFile >> TotalPoints;//storing data in Total Points
cout << LastName << endl;
// cout<<data<<endl; //print it out
}
myFile.close();
}
system("pause");
return 0;
}
Rather than checking if file is open or not a better approach is to check if file exist or not:
if(!myfile)
{
cout<<"error!file donot exist";
}