Publish and Subscribe Example

Subscriber

When acting as a subscriber of Value Space content the program creates a SubscriberDialog. This dialog contains a widget for setting the base path of the QValueSpaceSubscriber and a table for displaying all of the values directly under base path in the Value Space.

We declare two slots to propagate values from the Value Space to the dialog in response to change notifications from QValueSpaceSubscriber.

 private slots:
     void changeSubscriberPath();
     void subscriberChanged();

To read values from the Value Space we first create a QValueSpaceSubscriber and connect to the contentsChanged() signal.

We explicitly call our subscriberChanged() slot to populate the table with the initial values.

 void SubscriberDialog::changeSubscriberPath()
 {
     if (listWidget)
         listWidget->clear();
     else if (tableWidget)
         tableWidget->clearContents();

     if (!subscriber)
         subscriber = new QValueSpaceSubscriber(ui->basePath->text(), this);
     else
         subscriber->setPath(ui->basePath->text());

     connect(subscriber, SIGNAL(contentsChanged()), this, SLOT(subscriberChanged()));

     subscriberChanged();
 }

In response to the contentsChanged() signal we update all the values in the table.

 void SubscriberDialog::subscriberChanged()
 {
     QStringList subPaths = subscriber->subPaths();

     if (listWidget) {
         listWidget->clear();
     } else if (tableWidget) {
         tableWidget->clearContents();
         tableWidget->setRowCount(subPaths.count());
     }

     for (int i = 0; i < subPaths.count(); ++i) {
         QVariant v = subscriber->value(subPaths.at(i));

         if (listWidget) {
             const QString itemTemplate("%1 (%2)\n%3");

             QListWidgetItem *item =
                 new QListWidgetItem(itemTemplate.arg(subPaths.at(i), v.typeName(), v.toString()));
             item->setFlags(item->flags() & ~Qt::ItemIsEditable);
             listWidget->addItem(item);
         } else if (tableWidget) {
             QTableWidgetItem *pathItem = new QTableWidgetItem(subPaths.at(i));
             pathItem->setFlags(pathItem->flags() & ~Qt::ItemIsEditable);
             QTableWidgetItem *valueItem = new QTableWidgetItem(v.toString());
             valueItem->setFlags(valueItem->flags() & ~Qt::ItemIsEditable);
             QTableWidgetItem *typeItem = new QTableWidgetItem(v.typeName());
             typeItem->setFlags(typeItem->flags() & ~Qt::ItemIsEditable);

             tableWidget->setItem(i, 0, pathItem);
             tableWidget->setItem(i, 1, valueItem);
             tableWidget->setItem(i, 2, typeItem);
         }
     }
 }