Ask help about Mysql query in QML

[Yang Yi]

Hello everyone
I just start learning QML. I meet a problem. In C++, I use the mysql database, and in the QML, I hope to get the query result data value of the certain index.

This is my c++ code
(1) MySQLQuery class

class MySQLQuery : public QSqlQueryModel
{
Q_OBJECT
Q_PROPERTY(QString query READ queryStr WRITE setQueryStr NOTIFY queryStrChanged)
Q_PROPERTY(QStringList userRoleNames READ userRoleNames CONSTANT)

public:
using QSqlQueryModel::QSqlQueryModel;
QHash<int, QByteArray> roleNames() const
{
QHash<int, QByteArray> roles;
for (int i = 0; i < record().count(); i ++) {
roles.insert(Qt::UserRole + i + 1, record().fieldName(i).toUtf8());
}
return roles;
}

QVariant data(const QModelIndex &index, int role) const
{
    QVariant value;
    if (index.isValid()) {
        if (role < Qt::UserRole) {
            value = QSqlQueryModel::data(index, role);
        } else {
            int columnIdx = role - Qt::UserRole - 1;
            QModelIndex modelIndex = this->index(index.row(), columnIdx);
            value = QSqlQueryModel::data(modelIndex, Qt::DisplayRole);
        }
    }
    return value;
}

QString queryStr() const{
    return query().lastQuery();
}

void setQueryStr(const QString &query){
    if(queryStr() == query)
        return;
    setQuery(query);
    emit queryStrChanged();
}

QStringList userRoleNames() const {
    QStringList names;
    for (int i = 0; i < record().count(); i ++) {
        names << record().fieldName(i).toUtf8();
    }
    return names;
}

signals:
void queryStrChanged();
};

(2) main.cpp

int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
QGuiApplication app(argc, argv);

// qmlRegisterType<MySQLService>("MySQLAdd",1,0,"MySQLAdd");

bool a = sqlConnection();
qmlRegisterType<MySQLQuery>("MySQLQuery", 1, 0, "MySQLQuery");

QQmlApplicationEngine engine;
const QUrl url(QStringLiteral("qrc:/main.qml"));
QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                 &app, [url](QObject *obj, const QUrl &objUrl) {
    if (!obj && url == objUrl)
        QCoreApplication::exit(-1);
}, Qt::QueuedConnection);
engine.load(url);




return app.exec();

}

The following is my QML:

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15
import QtMultimedia 5.15
import MySQLQuery 1.0
Window {
id: mainWin
width: 1080
height: 768
visible: true

MySQLQuery{
id: main_SQLquery
query:mainStr_SQLquery
}

Timer{
    id:timer_coal_counter
    interval: 1000
    running: true
    repeat:true
    onTriggered: {
        mainStr_coal_SQLquery = "select * from coal_level where camera_id = 0 order by time desc LIMIT 0, 1"
       console.log("-----------", main_coal_SQLquery.rowCount())

        console.log("-----------", main_coal_SQLquery.record(0).value("camera_id").toInt())

    }

}

There is mistake that "TypeError: Property 'record' of object MySQLQuery(0x1b33108a880) is not a function"

I checked the record is the function of QSqlQueryModel, and MySQLQuery is a class of QSqlQueryModel

Could you kindly to help me. Thank you very much

[JonB]

@Yang-Yi
Please use the forum's Code tags to enclose blocks of code for people to read.

I know little about QML. And I am not sure that it would the cause the "Property 'record' of object MySQLQuery(0x1b33108a880) is not a function" you report, that may come from elsewhere. BUT

        mainStr_coal_SQLquery = "select * from coal_level where camera_id = 0 order by time desc LIMIT 0, 1"
       console.log("-----------", main_coal_SQLquery.rowCount())

        console.log("-----------", main_coal_SQLquery.record(0).value("camera_id").toInt())

mainStr_coal_SQLquery seems to be a (JavaScript?) string. How can you access main_coal_SQLquery.rowCount() or main_coal_SQLquery.record(0) from a string?

[Yang Yi]

@JonB. Thank you very much. I am very glad you can give me help.

I can get the result of:

 console.log("========", main_coal_SQLquery.rowCount())

but I can not the the result of

console.log("========", main_coal_SQLquery.record(0))

The mistake is "TypeError: Property 'record' of object MySQLQuery(0x18692474a90) is not a function"