Class Property

src/react/properties.py:12–53

class Property:
    def __init__(self, value=None):
        self._value = value
        self._observers = []
        self.bound = False

    def subscribe(self, observer):
        self._observers.append(observer)

    def unsubscribe(self, observer):
        self._observers.remove(observer)

    def set(self, new_value):
        if self.bound:
            raise Exception('Failed to set value to bound property')
        self._set_internal(new_value)

    def _set_internal(self, new_value):
        old_value = self._value

        if old_value == new_value:
            return

        self._value = new_value

        for observer in self._observers:
            observer(old_value, new_value)

    def get(self):
        return self._value

    def bind(self, another_property, map_function=None):
        def binder(old_value, new_value):
            if map_function:
                value = map_function(new_value)
            else:
                value = new_value

            self._set_internal(value)

        another_property.subscribe(binder)
        binder(None, another_property.get())


class ObservableList(UserList):