pyqt/further/mvc_5.py

import random
import sys
from collections import UserDict

from PyQt5.QtCore import QObject, pyqtSignal, Qt
from PyQt5.QtWidgets import QMainWindow, QApplication, QFormLayout, QLineEdit, QSpinBox, QComboBox, QPushButton, \
    QCheckBox, QWidget


class DataModelSignals(QObject):
    # Emit an "updated" signal when a property changes.
    updated = pyqtSignal()


class DataModel(UserDict):

    def __init__(self, *args, **kwargs):
        self.signals = DataModelSignals()
        super().__init__(*args, **kwargs)

    def __setitem__(self, key, value):
        previous = self.get(key)  # Get the existing value.
        super().__setitem__(key, value)
        if value != previous:  # There is a change
            self.signals.updated.emit()  # Emit the signal
            print(self)  # Show the current state.


model = DataModel(
    name="Johnina Smith",
    age=10,
    favorite_icecream="Vanilla",
    disable_details=False,
)


class Controller:
    """ Simple controller, which handles backups and other operations. """
    backups = []

    def capitalize(self):
        model["name"] = model["name"].upper()

    def store_backup(self):
        self.backups.append(model.copy())

    def restore_backup(self):
        if not self.backups:
            return
        random.shuffle(self.backups)
        backup = self.backups.pop()
        model.update(backup)  # Overwrite the data in the model
        print("RESTORE:", model)
        print("BACKUPS:", len(self.backups))

    def apply_title_case(self):
        model["name"] = model["name"].title()


controller = Controller()


class MainWindow(QMainWindow):

    def __init__(self):
        super().__init__()
        self.setWindowTitle("MVC Example")
        layout = QFormLayout()

        # Dictionary to store the form data, with default data.
        self.name = QLineEdit()
        self.name.textChanged.connect(self.on_name_changed)
        self.age = QSpinBox()
        self.age.setRange(0, 200)
        self.age.valueChanged.connect(self.on_age_changed)
        self.icecream = QComboBox()
        self.icecream.addItems(["Vanilla", "Strawberry", "Chocolate"])
        self.icecream.currentTextChanged.connect(self.on_icecream_changed)

        self.title_btn = QPushButton("Set Title Case")
        self.title_btn.pressed.connect(controller.apply_title_case)

        # tag::connect[]
        self.save_btn = QPushButton("Save")
        self.save_btn.pressed.connect(controller.store_backup)
        self.restore_btn = QPushButton("Restore")
        self.restore_btn.pressed.connect(controller.restore_backup)
        # end::connect[]

        self.disable_details = QCheckBox("Disable Details?")
        self.disable_details.toggled.connect(self.on_disable_details_toggled)

        layout.addRow("Name", self.name)
        layout.addRow(self.title_btn)
        layout.addRow("Age", self.age)
        layout.addRow("Favorite Ice Cream", self.icecream)
        layout.addWidget(self.disable_details)  # QCheckBox has its own label.
        layout.addRow(self.save_btn)
        layout.addRow(self.restore_btn)
        layout.setLabelAlignment(Qt.AlignLeft)

        widget = QWidget()
        widget.setLayout(layout)
        self.setCentralWidget(widget)

        self.update_ui()
        # Hook our UI sync into the model updated signal
        model.signals.updated.connect(self.update_ui)

    def update_ui(self):
        self.name.setText(model["name"])
        self.age.setValue(model["age"])
        self.icecream.setCurrentText(model["favorite_icecream"])
        self.disable_details.setChecked(model["disable_details"])

        self.age.setDisabled(model["disable_details"])
        self.icecream.setDisabled(model["disable_details"])

    def on_name_changed(self, name):
        model["name"] = name

    def on_age_changed(self, age):
        model["age"] = age

    def on_icecream_changed(self, icecream):
        model["favorite_icecream"] = icecream

    def on_disable_details_toggled(self, checked):
        model["disable_details"] = checked


if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())