Calling a method from a different .cpp file - qt

Question

I want to save some data as a text file, the first txt file will contain header information, the other text file will save data streamed from sensors, so with the help from the internet I created the following "datalogger.cpp" file
#include "datalogger.h"
#include <QDebug>
#include <iostream>
#include <QFile>
DataLogger::DataLogger(QObject *parent) : QObject(parent)
{
}
DataLogger::~DataLogger(){
}
void DataLogger::save(DataStream &input){
saveAsText(input);
}
void DataLogger::saveAsText(DataStream &input){
QTextStream outHeader(&outFileHeader);
outHeader << "[CAPTURE SETTINGS]\n"
<< "Filename: " << SettingsSingleton::instance().getFileName() << ".txt \n"
<< "Samples: " << QString::number(input.size()) << "\n"
<< "Duration: " << QString::number(input.back().time) << "ms \n"
<< "Sample rate: " << QString::number(SettingsSingleton::instance().getSampleRate()) << " Hz\n"
<< "Source: " << SettingsSingleton::instance().getSource() << "\n"
outFileHeader.close();
}
QFile outFile(SettingsSingleton::instance().getFileName() + ".txt");
QTextStream out(&outFile);
for (int i ; i<input.size();i++){
const EcgStreamObject tmp=input.at(i);
out << tmp.toText() << endl; //"\n";
}
outFile.close();
}
}
I have my "DataStream" input variable that I want to pass to the method and save as a ".txt" file, however I do no know how to call the method "void DataLogger::save(DataStream &input)" from a different ".cpp" file where the DataStream variable is located.
I am extremely new to c++ please it as simple as possible please.
Thank you in advance

Answer 1

If I get your question right, it is about how to create and use a header file in c++.
There is already a lot of information about this, for example this article from cplusplus.com or this from learncpp.com.

Answer 2

All you should need to do is add "datalogger.h" to your other file.
When you call the method DataLogger::save from your other file, the program will search for an implementation that was linked to your program (i.e. the file you posted here) and use that to actually perform the work.
Stefan's answer is probably important to look at too as it will cover this case and some other basics if you are going to be working in C/C++ long term.