Displaying JavaScript variable in QML

gabor53

Hi,
I am using the following code to get a value from an SQLite db:


function getLastID() {

    var lastID
    dbInit()

    var db = dbGetHandle()

    db.transaction(function (tx) {
        var ID = tx.executeSql(
                    'SELECT id FROM IDNumber ORDER BY id DESC LIMIT 1')

        for (var i = 0; i < ID.rows.length; i++) {
            lastID = ID.rows.item(i).id
            console.log("lastID: " + lastID)
        }
        return lastID
    })
}

The QML code to display lastID:

import QtQuick 2.9
import QtQuick.Window 2.2
import QtQuick.LocalStorage 2.0
import QtQuick.Layouts 1.3
import QtQml.Models 2.3
import QtQuick.Controls 2.2
import "Database.js" as JS

Window {
    visible: true
    width: 640
    height: 480

    property var newID: JS.getLastID()

    Text {
        id: sorszam
        text: newID
    }
}

When I run it, I get the following messages:
lastID: 1 //this is correct
file:Counter//main.qml: Unable to assign (undefined) to QString.
What is the correct way of doing this?
Thank you for your help.

raven-worx

@gabor53 said in Displaying JavaScript variable in QML:

file:Counter//main.qml: Unable to assign (undefined) to QString.

where is the code of this line?

Beside that, your getLastID() function does not return a value (undefined). Only your inner function does

gabor53

Hi @raven-worx ,
The line is

text: newID

How can I get the outer function return lastID?
Thank you.

raven-worx

@gabor53
you should do db.readTransaction(callback(tx)) and return the result object itself or the desired value of it.
(see https://doc.qt.io/qt-5.6/qtquick-localstorage-qmlmodule.html)