**Course Title:** PySide6 Application Development **Section Title:** Model-View-Controller (MVC) Architecture **Topic:** Building an app with custom list and table models.(Lab topic) **Overview:** In this lab topic, you will learn how to build a PySide6 application using custom list and table models. You will implement a simple note-taking app that allows users to create, read, update, and delete notes. You will use the QAbstractListModel and QAbstractTableModel classes to create custom models for your list and table views. **Objectives:** * Understand how to create custom list and table models using QAbstractListModel and QAbstractTableModel. * Learn how to implement the MVC architecture in a PySide6 application. * Understand how to use custom models with QListView and QTableView. * Learn how to implement CRUD operations (Create, Read, Update, Delete) using custom models. **Custom List Model:** To create a custom list model, you need to subclass QAbstractListModel and implement the following methods: * data() * rowCount() * flags() * setData() Here is an example implementation of a custom list model for a note-taking app: ```python from PySide6.QtCore import QAbstractListModel, Qt class NoteListModel(QAbstractListModel): def __init__(self, notes=None): super().__init__() self.notes = notes if notes else [] def data(self, index, role): if role == Qt.DisplayRole: return self.notes[index.row()] def rowCount(self, parent=None): return len(self.notes) def flags(self, index): return Qt.ItemIsEnabled | Qt.ItemIsSelectable def setData(self, index, value, role): if role == Qt.EditRole: self.notes[index.row()] = value return True return False ``` **Custom Table Model:** To create a custom table model, you need to subclass QAbstractTableModel and implement the following methods: * data() * rowCount() * columnCount() * flags() * setData() Here is an example implementation of a custom table model for a note-taking app: ```python from PySide6.QtCore import QAbstractTableModel, Qt class NoteTableModel(QAbstractTableModel): def __init__(self, notes=None): super().__init__() self.notes = notes if notes else [] def data(self, index, role): if role == Qt.DisplayRole: return self.notes[index.row()]["text"] def rowCount(self, parent=None): return len(self.notes) def columnCount(self, parent=None): return 2 def flags(self, index): return Qt.ItemIsEnabled | Qt.ItemIsSelectable def setData(self, index, value, role): if role == Qt.EditRole: self.notes[index.row()]["text"] = value return True return False ``` **Implementing MVC Architecture:** To implement the MVC architecture, you need to create a model, a view, and a controller. * The model is responsible for managing the data. * The view is responsible for displaying the data. * The controller is responsible for handling the user interactions and updating the model and view accordingly. Here is an example implementation of the MVC architecture for a note-taking app: ```python from PySide6.QtWidgets import QApplication, QListView, QTableView class NoteApp(QApplication): def __init__(self): super().__init__() def createModel(self): self.model = NoteListModel() def createView(self): self.listView = QListView() self.tableView = QTableView() def createController(self): self.controller = NoteController(self.model, self.listView, self.tableView) class NoteController: def __init__(self, model, listView, tableView): self.model = model self.listView = listView self.tableView = tableView def addNote(self, text): self.model.notes.append(text) self.model.layoutChanged.emit() def updateNote(self, index, text): self.model.notes[index] = text self.model.layoutChanged.emit() def deleteNote(self, index): del self.model.notes[index] self.model.layoutChanged.emit() ``` **Using Custom Models with QListView and QTableView:** To use custom models with QListView and QTableView, you need to set the model property of the view: ```python self.listView.setModel(self.model) self.tableView.setModel(self.model) ``` **Implementing CRUD Operations:** To implement CRUD operations, you need to create buttons for adding, updating, and deleting notes. You can use the signals and slots mechanism to connect the buttons to the controller methods: ```python from PySide6.QtWidgets import QPushButton class NoteApp(QApplication): def __init__(self): super().__init__() self.createModel() self.createView() self.createController() self.addButton = QPushButton("Add Note") self.addButton.clicked.connect(self.controller.addNote) self.updateButton = QPushButton("Update Note") self.updateButton.clicked.connect(self.controller.updateNote) self.deleteButton = QPushButton("Delete Note") self.deleteButton.clicked.connect(self.controller.deleteNote) ``` **Conclusion:** In this lab topic, you learned how to build a PySide6 application using custom list and table models. You implemented a simple note-taking app that allows users to create, read, update, and delete notes. You used the QAbstractListModel and QAbstractTableModel classes to create custom models for your list and table views. You implemented the MVC architecture and used custom models with QListView and QTableView. **Practical Takeaways:** * Use custom models to manage complex data structures. * Implement the MVC architecture to separate concerns and improve maintainability. * Use QListView and QTableView to display data in a user-friendly way. * Implement CRUD operations using custom models and views. **External Resources:** * [Qt Documentation: QAbstractListModel](https://doc.qt.io/qtforpython-6/PySide6/QtCore/QAbstractListModel.html) * [Qt Documentation: QAbstractTableModel](https://doc.qt.io/qtforpython-6/PySide6/QtCore/QAbstractTableModel.html) * [Qt Tutorial: Model-View-Controller](https://doc.qt.io/qtforpython-6/tutorials/modelview/controller.html) **Leave a Comment or Ask for Help:** If you have any questions or need help with implementing custom models and MVC architecture in your PySide6 application, leave a comment below or [contact us](mailto:support@example.com).