Read local xml file

[KeineAhnung]

Hi,

finally I managed to download and save a xml file to my disk. Now I would like to find a specific element in this xml file. I managed to open it in QML using JS (how to) but I am just not able to access the content of the nodes. What is the right syntax to access these information from the for loop?

<xml>
 <termin type="1">
  <datum>1449939600</datum>
  <art>BA</art>
  <thema>Feier</thema>
  <anmerkung/>
 </termin>
 <termin type="2">
  <datum>1450458000</datum>
  <art>Supervision</art>
  <thema>Supervision</thema>
  <anmerkung/>
</termin>
</xml>

<xml>
 <termin type="1">
  <datum>1449939600</datum>
  <art>BA</art>
  <thema>Feier</thema>
  <anmerkung/>
 </termin>
 <termin type="2">
  <datum>1450458000</datum>
  <art>Supervision</art>
  <thema>Supervision</thema>
  <anmerkung/>
</termin>
</xml>

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For example console.log(a[ii].getElementsByTagName("datum")[0].childNodes[0].nodeValue); says TypeError: Cannot call method 'getElementsByTagName' of undefined
What am I doing wrong?

[anda_skoa]

The easiest way from QML is XmlListModel.

Cheers,
_

[KeineAhnung]

Also if I am looking for a specific value in the XML file?

By the way I just got it. The right syntax to access the datum would be:

console.log(a.childNodes[ii].childNodes[0].firstChild.nodeValue);

console.log(a.childNodes[ii].childNodes[0].firstChild.nodeValue);

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[anda_skoa]

Also if I am looking for a specific value in the XML file?

Then the most efficient way is to use the QXmlStreamReader API.
Creating a full DOM structure just for getting a single value would be quite an overkill

But of course that requires to have a C++ application core available.
Since you pointed to the XML RPC Request example I guess that is not the case for you, otherwise you would not be doing data processing in JavaScript

Cheers,
_

[KeineAhnung]

I am working on a Sailfish OS app so I could use C++. For the moment it is working and my XML file will have not more than 100 entries. But I will look at QXmlStreamReader.
Are you familiar with Sailfish OS?

Thanks for the hint.

[anda_skoa]

I am working on a Sailfish OS app so I could use C++.

Then the usual recommendation stands: don't use JavaScript for data processing that is not UI related.
Keep JS usage as minimal as possible.

For the moment it is working and my XML file will have not more than 100 entries.

So you need one value from each of these 100 entries?
And you are not needing these 100 values as a model?

- Extractnig values into a list or vector: QXmlStreamReader
- Needing the values only as a model in QML: XmlListModel

Are you familiar with Sailfish OS?

Haven't worked with it myself but I have heard about it.
It is the system used by Jolla, an embedded Linux using a Qt base application framework, with Wayland as the display technology.

Cheers,
_

[KeineAhnung]

The XML file contains dates and I want to display upcoming date on the first page. The JS is very fast I cannot see any delay but I will rework my xmlFileHandler class and add the option to extract the next event. Understand I correctly that you would put the XML file content into a QVector and than search through that?

By the way, I noticed a difference between JS and XmlListView. Within XmlListView my timestamps are not displayed correctly. I use the exact same code to convert the same timeStamp from the XML file. 6pm is displayed correctly but all other times are off a few seconds.

Qt.formatDateTime(new Date(timeStamp,"dd.MM.yyyy - hh:mm" );

Qt.formatDateTime(new Date(timeStamp,"dd.MM.yyyy - hh:mm" );

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Is this a known issue?

[anda_skoa]

The JS is very fast I cannot see any delay

Avoiding JS it not only about performance, it is mostly about correctness and code maintainability.

Understand I correctly that you would put the XML file content into a QVector and than search through that?

Yes, if you extract a list of timestamps, I would store them in a vector or list of QDateTime.

By the way, I noticed a difference between JS and XmlListView. Within XmlListView my timestamps are not displayed correctly. I use the exact same code to convert the same timeStamp from the XML file. 6pm is displayed correctly but all other times are off a few seconds.

Qt.formatDateTime(new Date(timeStamp,"dd.MM.yyyy - hh:mm" );

Qt.formatDateTime(new Date(timeStamp,"dd.MM.yyyy - hh:mm" );

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Is this a known issue?

The timeStamp value being the same in both cases?

Cheers,
_

[KeineAhnung]

Yes it is the same timestamp. I have the date in two locations. On the first page it is correct and on the full list page it is off.

How would you put the xml file into the vector? All code examples I have found look like this:

while(!xml.atEnd() && !xml.hasError())
{
    /* Read next element.*/
    QXmlStreamReader::TokenType token = xml.readNext();
    /* If token is just StartDocument, we'll go to next.*/
    if(token == QXmlStreamReader::StartDocument)
        continue;
 
    /* If token is StartElement, we'll see if we can read it.*/
    if(token == QXmlStreamReader::StartElement) {
        if(xml.name() == "email") {
            ui->listWidget->addItem("Element: "+xml.name().toString());
            continue;
        }
    }
}
/* Error handling. */
if(xml.hasError())
    QMessageBox::critical(this, "QXSRExample::parseXML", xml.errorString(), QMessageBox::Ok);
 
//resets its internal state to the initial state.
xml.clear();
}

while(!xml.atEnd() && !xml.hasError())
{
    /* Read next element.*/
    QXmlStreamReader::TokenType token = xml.readNext();
    /* If token is just StartDocument, we'll go to next.*/
    if(token == QXmlStreamReader::StartDocument)
        continue;

    /* If token is StartElement, we'll see if we can read it.*/
    if(token == QXmlStreamReader::StartElement) {
        if(xml.name() == "email") {
            ui->listWidget->addItem("Element: "+xml.name().toString());
            continue;
        }
    }
}
/* Error handling. */
if(xml.hasError())
    QMessageBox::critical(this, "QXSRExample::parseXML", xml.errorString(), QMessageBox::Ok);

//resets its internal state to the initial state.
xml.clear();
}

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So if I go through the XML one by one I could also stop when I found what I was looking for without putting all elements into the vector.

[ChrisW67]

The formatDateTime() call you gives you a string representing the time stamp to an accuracy of minutes. How do you tell the value is "off a few seconds"?

[KeineAhnung]

For debugging I also displayed the seconds and saw that different timeStamps have different offsets. So 7pm is always off 16s 6pm is okay 19:30 is off 22s and so on.

[anda_skoa]

How would you put the xml file into the vector?

Not the XML file, the data you are interested in.
In the example that would be instead of line

ui->listWidget->addItem("Element: "+xml.name().toString());

ui->listWidget->addItem("Element: "+xml.name().toString());

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So if I go through the XML one by one I could also stop when I found what I was looking for without putting all elements into the vector.

Of course.
That's one of the great things about QXmlStreamReader.

Cheers,
_