Hello Word! example of qt-mvvm library.

This explains how to create a model, add property items to it, implement simple business logic, and show the content of the model in Qt widgets by adapting it for QAbstractItemModel interface.

In this example, the main window contains a tree view with a simple model in it. The content of one cell is reacting to changes in another cell. This was achieved in the following way:

First, SessionModel is created, single CompountItem is inserted to it.

SessionModel model;
auto item = model.insertItem<CompoundItem>();
item->setDisplayName("Item");

We add two property items to it. One property with the name Hello is intended to store std::string with current value World!. The second property has a name Your answer is and intended to store bool values, with current value true.

item->addProperty("Hello", "World!");
item->addProperty("Your answer is", true);

Next, we create callback which will be triggered each time item's properties are changing. In this particular case, we will update the value of the property Your answer is depending on whether the value of the property with the name Hello is equal to World!, or not.

auto on_property = [](SessionItem* item, const std::string& name) {
    if (name == "Hello")
        item->setProperty("Your answer is", item->property<std::string>("Hello") == "World!");
};
item->mapper()->setOnPropertyChange(on_property, nullptr);

Finally, we show the content of the model in QTreeView. We create DefaultViewModel to adapt content of SessionModel to QAbstractItemModel interface with one-to-one layout. And we create a delegate to get a fancy editor for bool values.

DefaultViewModel viewmodel(&model);
ViewModelDelegate delegate;

Finally, let's initialize the tree with a view model and delegate.

QTreeView view;
view.setModel(&viewmodel);
view.setItemDelegate(&delegate);
view.show();