// Copyright (C) 2016 The Qt Company Ltd. // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0 #include "main.h" #include MyMain::MyMain(QWidget *parent, Qt::WFlags flags) : QWidget(parent, flags) { ui.setupUi(this); connect(ui.comboBox, QOverload::of(&QComboBox::currentIndexChanged), this, &MyMain::select); } void MyMain::add(IComboEntry *obj) { m_entries.append(obj); ui.comboBox->addItem(obj->title()); } void MyMain::select(int index) { IComboEntry *entry = m_entries.at(index); // with multiple inheritance we would use qobject_cast here // instead we use query, to get the components if they exist IText1 *t1 = Aggregation::query(entry); IText2 *t2 = Aggregation::query(entry); IText3 *t3 = Aggregation::query(entry); // set the label texts and enable/disable, depending on whether // the respective interface implementations exist const QString na("N/A"); ui.text1->setText(t1 ? t1->text() : na); ui.text2->setText(t2 ? t2->text() : na); ui.text3->setText(t3 ? t3->text() : na); ui.text1->setEnabled(t1); ui.text2->setEnabled(t2); ui.text3->setEnabled(t3); } MyMain::~MyMain() { // the following deletes all the Aggregate and IComboEntry and ITextX // objects, as well as any other components we might have added qDeleteAll(m_entries); } int main(int argc, char *argv[]) { QApplication app(argc, argv); MyMain w; // create and set up some objects // the first does only implement the required IComboEntry // we don't need an aggregation for this IComboEntry *obj1 = new IComboEntry("Entry without text"); // the second additionally provides an IText2 implementation // adding a component to the aggregation is done by setting the aggregation as the parent of the component Aggregation::Aggregate *obj2 = new Aggregation::Aggregate; obj2->add(new IComboEntry("Entry with text 2")); obj2->add(new IText2("This is a text for label 2")); // and so on... two more objects... Aggregation::Aggregate *obj3 = new Aggregation::Aggregate; obj3->add(new IComboEntry("Entry with text 1 and 2")); obj3->add(new IText1("I love Qt!")); obj3->add(new IText2("There are software companies...")); Aggregation::Aggregate *obj4 = new Aggregation::Aggregate; obj4->add(new IComboEntry("Entry with text 1 and 3")); obj4->add(new IText1("Some text written here.")); obj4->add(new IText3("I'm a troll.")); // the API takes IComboEntries, so we convert the them to it // the MyMain object takes the ownership of the whole aggregations w.add(Aggregation::query(obj1)); w.add(Aggregation::query(obj2)); w.add(Aggregation::query(obj3)); w.add(Aggregation::query(obj4)); w.show(); return app.exec(); }