Class ConfigValueAssociation

examples/versioned_rows/versioned_map.py:153–196

Relate ConfigData objects to associated ConfigValue objects.

class ConfigValueAssociation(Base):
    """Relate ConfigData objects to associated ConfigValue objects."""

    __tablename__ = "config_value_association"

    config_id = Column(ForeignKey("config.id"), primary_key=True)
    """Reference the primary key of the ConfigData object."""

    config_value_id = Column(ForeignKey("config_value.id"), primary_key=True)
    """Reference the primary key of the ConfigValue object."""

    config_value = relationship("ConfigValue", lazy="joined", innerjoin=True)
    """Reference the related ConfigValue object."""

    def __init__(self, config_value):
        self.config_value = config_value

    def new_version(self, session):
        """Expire all pending state, as ConfigValueAssociation is immutable."""

        session.expire(self)

    @property
    def name(self):
        return self.config_value.name

    @property
    def value(self):
        return self.config_value.value

    @value.setter
    def value(self, value):
        """Intercept set events.

        Create a new ConfigValueAssociation upon change,
        replacing this one in the parent ConfigData's dictionary.

        If no net change, do nothing.

        """
        if value != self.config_value.value:
            self.config_data.elements[self.name] = ConfigValueAssociation(
                ConfigValue(self.config_value.name, value)
            )


class ConfigValue(Base):