Qt. get part of QString

I want to get QString from another QString, when I know necessary indexes. For example: Main string: "This is a string". I want to create new QString from first 5 symbols and get "This ".
input : first and last char number.
output : new QString.

How to create it ?

P.S. Not only first several letters, also from the middle of the line, for example from 5 till 8.

If you do not need to modify the substring, then you can use QStringRef. The QStringRef class is a read only wrapper around an existing QString that references a substring within the existing string. This gives much better performance than creating a new QString object to contain the sub-string. E.g.

QString myString("This is a string");
QStringRef subString(&myString, 5, 2); // subString contains "is"

If you do need to modify the substring, then left(), mid() and right() will do what you need...

QString myString("This is a string");
QString subString = myString.mid(5,2); // subString contains "is"
subString.append("n't"); // subString contains "isn't"

Use the left function:

QString yourString = "This is a string";
QString leftSide = yourString.left(5);
qDebug() << leftSide; // output "This "

Also have a look at mid() if you want more control.