SofaVc

class ReactNumber(Observerble, Observer):
    def __init__(self, number: Union[int, float, Strategy]):
        super().__init__(number)
        self.value = number

    @property
    def value(self) -> Union[int, float]:
        if self._number is None and self._strategy is not None:
            self._number = self._strategy.eval()
        return self._number