C++ Qt - Reading specific portion of a text file - c++

Question

I want to read a specific portion of a text file in a list widget. I have try different ways and looked online for some solutions but I couldn't find much. Im new using Qt but getting along well with it for the most part.
QFile YearInfo("C:/Users/Documents/info.txt");
YearInfo.open(QIODevice::ReadWrite | QIODevice::Text);
if(YearInfo.isOpen()){
QTextStream in(&YearInfo);
bool readEnabled = false;
QString outputText, startToken = line, endToken = "*"; // line = "2019"
while(!in.atEnd()){
QString getLine = in.readLine();
if(getLine == endToken){
readEnabled = false;
}
if(readEnabled){
outputText.append(getLine + "\n");
}
if(getLine == startToken){
readEnabled = true;
}
}
ui->listWidget->addItem(outputText);
}
YearInfo.flush();
YearInfo.close();
Text File contains:
2019
Position Division Title Date (W.M./R.M./J.R)
*
2020
Position Division Title Date (P.M./V.R/S.T)
*

Answer 1

The code that you have written works as long as you are trying to extract a section of text formatted in the following way
2019
Position Division Title <~~ this line is extracted
Date (W.M./R.M./J.R) <~~ this line is extracted
More stuff <~~ this line is extracted
*
If you have something formatted in the following way
2019 Position Division
Title Date (W.M./R.M./J.R) *
2019 Position Division Title Date (W.M./R.M./J.R) *
nothing will be extracted because you start the extraction when you find a line that contains only the startToken. Same thing for the end token.
You could try to modify the while loop in your code in the following way
while(!in.atEnd()){
QString getLine = in.readLine().trimmed();
if(getLine.startsWith(startToken)){
readEnabled = true;
}
if(readEnabled){
outputText.append(getLine + "\n");
}
if(getLine.endsWith(endToken)){
readEnabled = false;
}
}
Now you are checking if the line startsWith the startToken. Here I also added a trimmed instruction to remove white spaces at the beginning and at the end of each line (just in case...). The same thing is done with endsWith for the endToken.
Also it would be best to open the device in read-only mode, since you are not modifying it anyway
YearInfo.open(QIODevice::ReadOnly | QIODevice::Text);
and also the flush at the end is redundant.
Hope this helps =)

Answer 2

To find the entry of a string, I use QRegExp. Please note that since you have a stopToken like a special symbol for QRegExp it might be changed for "\*:
#include <QRegExp>
#include <QDebug>
QStringList tokenize(QString line, QString start, QString end)
{
QRegExp rx(start+".*"+end);
rx.indexIn(line);
return rx.capturedTexts();
}
void test()
{
qDebug()<<tokenize("2019 Position Division Title Date (W.M./R.M./J.R) *", "2019", "\\*");
// returned ("2019 Position Division Title Date (W.M./R.M./J.R) *")
qDebug()<<tokenize("2020 Position Division Title Date (P.M./V.R/S.T) *", "2019", "\\*");
// returned ("")
}
Your function must be look like this:
...
while(!in.atEnd()){
QString getLine = in.readLine();
QStringList strL = tokenize(getLine, startToken, stopToken);
if (strL.size())
ui->listWidget->addItem(strL[0]);
}

Answer 3

QFile YearInfo("C:/Users/Documents/info.txt");
YearInfo.open(QIODevice::ReadOnly | QIODevice::Text);
if(YearInfo.isOpen()){
QTextStream in(&YearInfo);
bool readEnabled = false;
QString outputText = "", startToken = line.trimmed(), endToken = "*";
while(!in.atEnd()){
QString getLine = in.readLine().trimmed();
if(getLine == startToken){
readEnabled = true;
}
if(readEnabled){
outputText.append(getLine + "\n");
}
if(getLine == endToken){
readEnabled = false;
}
}
ui->listWidget->addItem(outputText);
}
YearInfo.close();