Method bind

returns/context/requires_context.py:176–209

Composes a container with a function returning another container. This is useful when you do several computations that rely on the same context. .. code:: python >>> from returns.context import RequiresContext >>> def first(lg: bool) -> Requir

(
        self,
        function: Callable[
            [_ReturnType_co],
            Kind2[RequiresContext, _NewReturnType, _EnvType_contra],
        ],
    )

        )

    def bind(
        self,
        function: Callable[
            [_ReturnType_co],
            Kind2[RequiresContext, _NewReturnType, _EnvType_contra],
        ],
    ) -> RequiresContext[_NewReturnType, _EnvType_contra]:
        """
        Composes a container with a function returning another container.

        This is useful when you do several computations that rely on the
        same context.

        .. code:: python

          >>> from returns.context import RequiresContext

          >>> def first(lg: bool) -> RequiresContext[int, float]:
          ...     # `deps` has `float` type here:
          ...     return RequiresContext(
          ...         lambda deps: deps if lg else -deps,
          ...     )

          >>> def second(number: int) -> RequiresContext[str, float]:
          ...     # `deps` has `float` type here:
          ...     return RequiresContext(
          ...         lambda deps: '>=' if number >= deps else '<',
          ...     )

          >>> assert first(True).bind(second)(1) == '>='
          >>> assert first(False).bind(second)(2) == '<'

        """
        return RequiresContext(lambda deps: dekind(function(self(deps)))(deps))

    #: Alias for `bind_context` method, it is the same as `bind` here.
    bind_context = bind