QAbstractItemModel question

[awhite1159]

I am using the QAbstractItemModel and below is the implementation of the data function. I would like to keep my current data structure separate and intact so that is why I chose the abstract rather than the standard. The problem I am having is that I am not sure if I am re-inventing the wheel. Does this code seem unusual and unnecessary? Would I have an easier time using the QStandardItemModel along with a subclassed QStandardItem?

(BUS is a namespace where I defined the icon type ids. I also created a member in my BUSDataMover object that stores the icon type which can be obtained with getIconType())

QVariant TreeModel::data(const QModelIndex &index, int role) const {
	if(!index.isValid())
		return QVariant();
	BUSDataMover* item;
	switch(role) {
		case Qt::DisplayRole:
			item = static_cast<BUSDataMover*>(index.internalPointer());
			return item->data(index.column());
			break;
		case Qt::DecorationRole:
			item = static_cast<BUSDataMover*>(index.internalPointer());
			if(index.column() != 0)
				return QVariant();
			switch(item->getIconType()) {
				case BUS::NetworkIcon:
					return QIcon(":/images/network.png");
					break;
				case BUS::ClientIcon:
					return QIcon(":images/client.png");
					break;
				case BUS::ServerIcon:
					return QIcon(":images/server.png");
					break;
				case BUS::NICIcon:
					return QIcon(":images/nic.png");
				default:
					return QIcon(":/images/unknown.png");
			}
			break;
		default:
			return QVariant();
	}
}

QVariant TreeModel::data(const QModelIndex &index, int role) const {
	if(!index.isValid())
		return QVariant();
	BUSDataMover* item;
	switch(role) {
		case Qt::DisplayRole:
			item = static_cast<BUSDataMover*>(index.internalPointer());
			return item->data(index.column());
			break;
		case Qt::DecorationRole:
			item = static_cast<BUSDataMover*>(index.internalPointer());
			if(index.column() != 0)
				return QVariant();
			switch(item->getIconType()) {
				case BUS::NetworkIcon:
					return QIcon(":/images/network.png");
					break;
				case BUS::ClientIcon:
					return QIcon(":images/client.png");
					break;
				case BUS::ServerIcon:
					return QIcon(":images/server.png");
					break;
				case BUS::NICIcon:
					return QIcon(":images/nic.png");
				default:
					return QIcon(":/images/unknown.png");
			}
			break;
		default:
			return QVariant();
	}
}

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[wysota]

It's fine, although using QStandardItemModel with a subclassed QStandardItem would be fine as well. In both cases you have to reimplement the data() method and a few others as well - fewer with the QStandardItem method, but if you already implemented the model then this doesn't really matter...

[awhite1159]

Thanks Wysota.

One more question. You mention that I could use QStandardItemModel and then subclass QStandardItem. If I were to do this, would I be able to provide a pointer to my custom data structure and then use QStandardItem::UserType for each of the columns in my custom data structure to set/get data?

[wysota]

Not exactly. UserType is a constant which marks the beginning of the id space for standard item subclasses. You should reimplement QStandardItem::type() and return a value greater than UserType that will uniquely identify your class, so that you can later identify the type of item (for instance when comparing items using operator<). This has nothing to do with structures or data. To return contents of your structure as different columns of the item you need to reimplement QStandardItem::data() and query your structure for particular piece of data for a particular column of the model. The same goes for QStandardItem::setData() if you want your item to be editable.