Subclassing QSqlTableModel insert new value - sql

Question

I want to show SQL data from a local db-File in a QML-Tableview and than would like to do some edits to the sql-database.
What I managed to do after about three weeks: Showing my data in a QML-Tableview. I am not sure if I really need to subclass QSqlTableModel and I definitly would be glad if subclassing would not be neccessary at all.
In my main.cpp following should create my model and directly add a record.
// Create an instance of the SqlModel for accessing the data
SqlDataModel *sqlModel;
sqlModel = new SqlDataModel(0,base.database());
sqlModel->setTable("diaBaneDatabase");
sqlModel->setSort(0, Qt::AscendingOrder);
sqlModel->setEditStrategy(QSqlTableModel::OnFieldChange);
sqlModel->select();
QSqlRecord record(sqlModel->record());
record.setValue(0,50);
record.setValue(3,222);
sqlModel->insertRecord(-1, record);
sqlModel->submitAll();
This should add 222 to the 4th column. But nothing will be stored in my sqlDatabase
My SqlDataModel::setData loolks like this:
bool SqlDataModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
qDebug() << index.column() << " " << index.row() << " " << value << " ---- " << role;
qDebug() << roles[Qt::UserRole + 1];
//qDebug() << QSqlTableModel::setData(modelIndex, value);
qDebug() << QSqlQueryModel::setData(index, value);
return false;
}
The output will be:
0 39 QVariant(int, 50) ---- 2
"id"
false
1 39 QVariant(QString, "") ---- 2
"id"
false
2 39 QVariant(QString, "") ---- 2
"id"
false
3 39 QVariant(int, 222) ---- 2
"id"
false
4 39 QVariant(double, 0) ---- 2
"id"
false
5 39 QVariant(int, 0) ---- 2
"id"
false
6 39 QVariant(double, 0) ---- 2
"id"
false
7 39 QVariant(double, 0) ---- 2
"id"
false
For sure my setData method is wrong but I don't understand what should happen there and I didn't find any example for this.
Am I wrong with my assumption that I need to subclass QSqlTableModel to be able to put the model through QQmlContext to QML and than show the columns with roles named like my column-namings? If not how could I put the content of column 1 to QMLTableview:
TableViewColumn {
role: "id" // what should be the role if I don't subclass???
title: "ID"
width: 80
}
I'm happy for any help, comment, example, other posts or whatever brings me further forward ... thanks

Answer 1

I've been working on an example.
Some notes:
QML items such as TableView require a model so I think a QSqlTableModel is a very good option. Of course, you have other models that could be used to handle items of data.
In the class MySqlTableModel you will see the required role names. MySqlTableModel reimplements roleNames() to expose the role names, so that they can be accessed via QML.
You could reimplement the setData method in MySqlTableModel, but I think it is better to use the method insertRecord provided by QSqlTableModel.
I hope this example will help you to fix your errors.
main.cpp
#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include "mysqltablemodel.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("mydb");
if(!db.open()) {
qDebug() << db.lastError().text();
return 0;
}
QSqlQuery query(db);
if(!query.exec("DROP TABLE IF EXISTS mytable")) {
qDebug() << "create table error: " << query.lastError().text();
return 0;
}
if(!query.exec("CREATE TABLE IF NOT EXISTS mytable \
(id integer primary key autoincrement, name varchar(15), salary integer)")) {
qDebug() << "create table error: " << query.lastError().text();
return 0;
}
MySqlTableModel *model = new MySqlTableModel(0, db);
model->setTable("mytable");
model->setEditStrategy(QSqlTableModel::OnManualSubmit);
model->select();
QSqlRecord rec = model->record();
rec.setValue(1, "peter");
rec.setValue(2, 100);
model->insertRecord(-1, rec);
rec.setValue(1, "luke");
rec.setValue(2, 200);
model->insertRecord(-1, rec);
if(model->submitAll()) {
model->database().commit();
} else {
model->database().rollback();
qDebug() << "database error: " << model->lastError().text();
}
QQmlApplicationEngine engine;
QQmlContext *ctxt = engine.rootContext();
ctxt->setContextProperty("myModel", model);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
return app.exec();
}
mysqltablemodel.h
#ifndef MYSQLTABLEMODEL_H
#define MYSQLTABLEMODEL_H
#include <QSqlTableModel>
#include <QSqlRecord>
#include <QSqlError>
#include <QSqlQuery>
#include <QDebug>
class MySqlTableModel : public QSqlTableModel
{
Q_OBJECT
public:
MySqlTableModel(QObject *parent = 0, QSqlDatabase db = QSqlDatabase());
Q_INVOKABLE QVariant data(const QModelIndex &index, int role=Qt::DisplayRole ) const;
Q_INVOKABLE void addItem(const QString &name, const QString &salary);
protected:
QHash<int, QByteArray> roleNames() const;
private:
QHash<int, QByteArray> roles;
};
#endif // MYSQLTABLEMODEL_H
mysqltablemodel.cpp
#include "mysqltablemodel.h"
MySqlTableModel::MySqlTableModel(QObject *parent, QSqlDatabase db): QSqlTableModel(parent, db) {}
QVariant MySqlTableModel::data ( const QModelIndex & index, int role ) const
{
if(index.row() >= rowCount()) {
return QString("");
}
if(role < Qt::UserRole) {
return QSqlQueryModel::data(index, role);
}
else {
return QSqlQueryModel::data(this->index(index.row(), role - Qt::UserRole), Qt::DisplayRole);
}
}
QHash<int, QByteArray> MySqlTableModel::roleNames() const
{
QHash<int, QByteArray> roles;
roles[Qt::UserRole + 1] = "name";
roles[Qt::UserRole + 2] = "salary";
return roles;
}
void MySqlTableModel::addItem(const QString &name, const QString &salary)
{
QSqlRecord rec = this->record();
rec.setValue(1, name);
rec.setValue(2, salary.toInt());
this->insertRecord(-1, rec);
if(this->submitAll()) {
this->database().commit();
} else {
this->database().rollback();
qDebug() << "database error: " << this->lastError().text();
}
}
main.qml
import QtQuick 2.4
import QtQuick.Controls 1.3
import QtQuick.Window 2.2
import QtQuick.Dialogs 1.2
ApplicationWindow {
title: qsTr("Hello World")
width: 640
height: 480
visible: true
TableView {
id: tableView
anchors.fill: parent
TableViewColumn {
role: "name"
title: "Name"
width: 200
}
TableViewColumn {
role: "salary"
title: "Salary"
width: 200
}
model: myModel
}
Button {
id: addButton
anchors.verticalCenter: parent.verticalCenter
text: "Add item"
onClicked: {
if (nameBox.text || salaryBox.text) {
myModel.addItem(nameBox.text, salaryBox.text)
}
}
}
TextField {
id: nameBox
placeholderText: "name"
anchors.verticalCenter: parent.verticalCenter
anchors.left: addButton.right
anchors.leftMargin: 5
}
TextField {
id: salaryBox
placeholderText: "salary"
anchors.verticalCenter: parent.verticalCenter
anchors.left: nameBox.right
anchors.leftMargin: 5
}
}