Question

I’m reading from an xml file and trying to parse the data to a double. It is reading the data and displays the appropriate string in the application output but wont convert from string to double. This is the section of code doing the conversion.

if ( !(imgDur = QString ( xmlReader->readElementText() ).toDouble()) ){
        imgDur = 10;
}

this returns the number 0. I get zero errors and the code compiles. Why wont this work? Thank you for you time.

The entire loop that reads the XML file

//Parse the XML until we reach end of it
    while(!xmlReader->atEnd() && !xmlReader->hasError()) {
            // Read next element
            QXmlStreamReader::TokenType token = xmlReader->readNext();
            //If token is just StartDocument - go to next
            if(token == QXmlStreamReader::StartDocument) {
                    continue;
            }
            //If token is StartElement - read it
            if(token == QXmlStreamReader::StartElement) {

                    if(xmlReader->name() == "time_delay") {
                        qWarning() << xmlReader->readElementText(); // OUTPUTS 15

                        if ( !(imgDur = QString (xmlReader->readElementText()).toDouble()  ) ){
                            qWarning() << "AS AN DOUBLE" << imgDur;  // OUTPUTS 0
                            imgDur = 10;
                        }

                    }

                    if(xmlReader->name() == "value") {
                        qWarning() << xmlReader->readElementText(); // OUTPUTS 8
                    }

            }
    }

Answer 1

The main problem of your code was this qWarning() << xmlReader->readElementText(); // OUTPUTS 15 line. QXmlReader::readElementText() moves xmlReader pointer to the end of the text node, so the readNext() will return EndElement of A instead of QXmlStreamReader::Characters token. So basicly readElementText does something like that (note that in the real implementation it is a lot more complicated, as it checks default behaviour, sets QXmlStreamReader internal data/status/token etc):

QString retval;
if(xmlReader->readNext() == QXmlStreamReader::Characters)
{
    retval = xmlReader->text().toString();
    xmlReader->readNext();
}
return retval;

So basicly second xmlReader->readElementText(); will always return empty QString, as the current token is not QXmlStreamReader::StartElement anymore