How to search for a string in a text file using Qt

Question

I'm trying to search for a string in a text file; my aim is to write it only if it isn't already written inside my text file.

Here's my function (I don't know how to put inside the while loop):

QFile MyFile("text.txt");
MyFile.open(QIODevice::ReadWrite);
QTextStream in (&MyFile);

while(!MyFile.atEnd())
  { //do something to search string inside }

MyFile.close();

How can I do that? From Qt's Help, method "contains" works with const variable only; can I use it to look for my string?

Answer 1

You can do the following:

[..]
QString searchString("the string I am looking for");
[..]
QTextStream in (&MyFile);
QString line;
do {
    line = in.readLine();
    if (!line.contains(searchString, Qt::CaseSensitive)) {
        // do something
    }
} while (!line.isNull());

Answer 2

In case of not large file

QFile MyFile("text.txt");
MyFile.open(QIODevice::ReadWrite);
QTextStream in (&MyFile);
const QString content = in.readAll();
if( !content.contains( "String" ) {
//do something
}
MyFile.close();

To not repeat other answers in case of larger files do as vahancho suggested