How to isolate an integer in a QString

Question

I have a QString of Gcode that will look like this:

T<some number> <and anything might come after it>

Currently, I'm using myString.midRef(1,1).toInt() to get the digit I want (I don't care about the rest of the line). However, this will not work if there is a two digit number, like so:

T12 ;blah blah blah

Is there a good / better way of doing this other than searching index by index to see where the number stops?

• There will always be a T in front of the number.
• There will always be a semicolon after the number if there is any other text after it, but there may not be a space in between the number and the semicolon.
• There may or may not be anything after the number at all.

Answer 1

Use regular expression to extract the number pattern, e.g.

int ib, ie, n;
QStringRef num;
ib = str.indexOf(QRegExp("T\\d+(\\s*;{1}.|$)"));
if (ib >= 0) {
    ib++;
    ie = str.indexOf(";", ib);
    n = ie >= ib ? ie - ib : -1; 
    num = str.midRef(ib, n);
}

Notes:

1. T\d+ match a pattern begins with T followed by one or more digit.
2. \s*;{1}.|$ match zero or more white spaces followed by semicolon plus any character OR exactly none in the last character.

Please note that in the above rule, "T123 " or "T123\n" won't match the pattern. If you want to allow white space, use the following:

QRegExp("T\\d+\\s*(;{1}.|$)")