Class link

traitlets/traitlets.py:275–359

Link traits from different objects together so they remain in sync. Parameters ---------- source : (object / attribute name) pair target : (object / attribute name) pair transform: iterable with two callables (optional) Data transformation between source and target and t

class link:
    """Link traits from different objects together so they remain in sync.

    Parameters
    ----------
    source : (object / attribute name) pair
    target : (object / attribute name) pair
    transform: iterable with two callables (optional)
        Data transformation between source and target and target and source.

    Examples
    --------
    >>> class X(HasTraits):
    ...     value = Int()

    >>> src = X(value=1)
    >>> tgt = X(value=42)
    >>> c = link((src, "value"), (tgt, "value"))

    Setting source updates target objects:
    >>> src.value = 5
    >>> tgt.value
    5
    """

    updating = False

    def __init__(
        self, source: t.Any, target: t.Any, transform: t.Iterable[FuncT] | None = None
    ) -> None:
        _validate_link(source, target)
        self.source, self.target = source, target
        if transform:
            self._transform, self._transform_inv = transform  # type:ignore[method-assign]
        self.link()

    def _transform(self, x: T) -> T:
        """default transform: no-op"""
        return x

    _transform_inv = _transform

    def link(self) -> None:
        try:
            setattr(
                self.target[0],
                self.target[1],
                self._transform(getattr(self.source[0], self.source[1])),
            )

        finally:
            self.source[0].observe(self._update_target, names=self.source[1])
            self.target[0].observe(self._update_source, names=self.target[1])

    @contextlib.contextmanager
    def _busy_updating(self) -> t.Any:
        self.updating = True
        try: