Class Ref

src/py/reactpy/reactpy/utils.py:19–59

Hold a reference to a value This is used in imperative code to mutate the state of this object in order to incur side effects. Generally refs should be avoided if possible, but sometimes they are required. Notes: You can compare the contents for two ``Ref`` objects using th

class Ref(Generic[_RefValue]):
    """Hold a reference to a value

    This is used in imperative code to mutate the state of this object in order to
    incur side effects. Generally refs should be avoided if possible, but sometimes
    they are required.

    Notes:
        You can compare the contents for two ``Ref`` objects using the ``==`` operator.
    """

    __slots__ = ("current",)

    def __init__(self, initial_value: _RefValue = _UNDEFINED) -> None:
        if initial_value is not _UNDEFINED:
            self.current = initial_value
            """The present value"""

    def set_current(self, new: _RefValue) -> _RefValue:
        """Set the current value and return what is now the old value

        This is nice to use in ``lambda`` functions.
        """
        old = self.current
        self.current = new
        return old

    def __eq__(self, other: object) -> bool:
        try:
            return isinstance(other, Ref) and (other.current == self.current)
        except AttributeError:
            # attribute error occurs for uninitialized refs
            return False

    def __repr__(self) -> str:
        try:
            current = repr(self.current)
        except AttributeError:
            # attribute error occurs for uninitialized refs
            current = "<undefined>"
        return f"{type(self).__name__}({current})"


def vdom_to_html(vdom: VdomDict) -> str: