**Course Title:** PySide6 Application Development **Section Title:** Model-View-Controller (MVC) Architecture **Topic:** Data binding between models and views ### Overview In the previous topic, we explored the concept of models in PySide6 using `QAbstractListModel` and `QAbstractTableModel`. Now, we will discuss one of the core aspects of the Model-View-Controller (MVC) architecture in PySide6: data binding between models and views. **What is Data Binding?** Data binding is the process of connecting a model's data to a view's display. It allows you to synchronize the data between the model and the view, ensuring that the data displayed in the view accurately reflects the data stored in the model. ### Understanding Models and Views in PySide6 In PySide6, a model is an instance of a class that inherits from `QAbstractItemModel`, such as `QAbstractListModel` or `QAbstractTableModel`. A view is a widget that displays the data from a model, such as `QListView` or `QTableView`. ### Data Binding Methods in PySide6 PySide6 provides several ways to bind data between models and views: #### 1. Using the `setModel()` Method You can bind a model to a view using the `setModel()` method. This method is available in most view widgets, such as `QListView` and `QTableView`. **Example Code:** ```python import sys from PySide6.QtCore import QAbstractTableModel, Qt from PySide6.QtWidgets import QApplication, QTableView, QAbstractItemView class MyModel(QAbstractTableModel): def __init__(self): super().__init__() self._data = [[1, 2, 3], [4, 5, 6]] def rowCount(self, parent=None): return len(self._data) def columnCount(self, parent=None): return len(self._data[0]) def data(self, index, role=Qt.DisplayRole): if role == Qt.DisplayRole: return self._data[index.row()][index.column()] app = QApplication() view = QTableView() model = MyModel() view.setModel(model) view.show() sys.exit(app.exec()) ``` In this example, we create a simple model `MyModel` that inherits from `QAbstractTableModel`. We then create a `QTableView` instance and bind the model to the view using the `setModel()` method. #### 2. Using Delegate Classes Delegate classes are used to customize the display of data in a view. You can use delegate classes to bind data between models and views. **Example Code:** ```python import sys from PySide6.QtCore import QAbstractTableModel, Qt from PySide6.QtWidgets import QApplication, QTableView, QStyledItemDelegate from PySide6.QtGui import QBrush, QColor class MyDelegate(QStyledItemDelegate): def paint(self, painter, option, index): value = index.model().data(index, Qt.DisplayRole) if value % 2 == 0: painter.setBrush(QBrush(QColor("red"))) else: painter.setBrush(QBrush(QColor("blue"))) painter.drawRect(option.rect) class MyModel(QAbstractTableModel): def __init__(self): super().__init__() self._data = [[1, 2, 3], [4, 5, 6]] def rowCount(self, parent=None): return len(self._data) def columnCount(self, parent=None): return len(self._data[0]) def data(self, index, role=Qt.DisplayRole): if role == Qt.DisplayRole: return self._data[index.row()][index.column()] app = QApplication() view = QTableView() model = MyModel() delegate = MyDelegate() view.setItemDelegate(delegate) view.setModel(model) view.show() sys.exit(app.exec()) ``` In this example, we create a delegate class `MyDelegate` that inherits from `QStyledItemDelegate`. We then create a `QTableView` instance and bind the model to the view using the `setModel()` method. We also set the delegate using the `setItemDelegate()` method. ### Key Takeaways * Data binding is the process of connecting a model's data to a view's display. * PySide6 provides several ways to bind data between models and views, including using the `setModel()` method and delegate classes. * You can customize the display of data in a view using delegate classes. **Practice Exercise** * Create a simple model that displays a list of numbers. * Use the `setModel()` method to bind the model to a `QListView` instance. * Create a delegate class to customize the display of the numbers in the list view. **Additional Resources** For more information on data binding in PySide6, refer to the [Qt Documentation](https://doc.qt.io/qtforpython-5/PySide6/QtCore/QAbstractItemModel.html). ### What's Next? In the next topic, we will discuss custom models and proxy models.