Class RunnableBranch<RunInput, RunOutput>

Class that represents a runnable branch. The RunnableBranch is initialized with an array of branches and a default branch. When invoked, it evaluates the condition of each branch in order and executes the corresponding branch if the condition is true. If none of the conditions are true, it executes the default branch.

Example

const branch = RunnableBranch.from([
[
(x: { topic: string; question: string }) =>
x.topic.toLowerCase().includes("anthropic"),
anthropicChain,
],
[
(x: { topic: string; question: string }) =>
x.topic.toLowerCase().includes("langchain"),
langChainChain,
],
generalChain,
]);

const fullChain = RunnableSequence.from([
{
topic: classificationChain,
question: (input: { question: string }) => input.question,
},
branch,
]);

const result = await fullChain.invoke({
question: "how do I use LangChain?",
});

Type Parameters

  • RunInput = any

  • RunOutput = any

Hierarchy

  • Runnable<RunInput, RunOutput>
    • RunnableBranch

Constructors

Properties

branches: Branch<RunInput, RunOutput>[]
default: Runnable<RunInput, RunOutput, RunnableConfig>
name?: string

Methods

  • Create a new runnable sequence that runs each individual runnable in series, piping the output of one runnable into another runnable or runnable-like.

    Type Parameters

    • NewRunOutput

    Parameters

    • coerceable: RunnableLike<RunOutput, NewRunOutput>

      A runnable, function, or object whose values are functions or runnables.

    Returns Runnable<RunInput, Exclude<NewRunOutput, Error>, RunnableConfig>

    A new runnable sequence.

  • Stream all output from a runnable, as reported to the callback system. This includes all inner runs of LLMs, Retrievers, Tools, etc. Output is streamed as Log objects, which include a list of jsonpatch ops that describe how the state of the run has changed in each step, and the final state of the run. The jsonpatch ops can be applied in order to construct state.

    Parameters

    Returns AsyncGenerator<RunLogPatch, any, unknown>

  • Default implementation of transform, which buffers input and then calls stream. Subclasses should override this method if they can start producing output while input is still being generated.

    Parameters

    • generator: AsyncGenerator<RunInput, any, unknown>
    • options: Partial<RunnableConfig>

    Returns AsyncGenerator<RunOutput, any, unknown>

  • Bind lifecycle listeners to a Runnable, returning a new Runnable. The Run object contains information about the run, including its id, type, input, output, error, startTime, endTime, and any tags or metadata added to the run.

    Parameters

    • params: {
          onEnd?: ((run, config?) => void | Promise<void>);
          onError?: ((run, config?) => void | Promise<void>);
          onStart?: ((run, config?) => void | Promise<void>);
      }

      The object containing the callback functions.

      • Optional onEnd?: ((run, config?) => void | Promise<void>)
          • (run, config?): void | Promise<void>
          • Called after the runnable finishes running, with the Run object.

            Parameters

            Returns void | Promise<void>

      • Optional onError?: ((run, config?) => void | Promise<void>)
          • (run, config?): void | Promise<void>
          • Called if the runnable throws an error, with the Run object.

            Parameters

            Returns void | Promise<void>

      • Optional onStart?: ((run, config?) => void | Promise<void>)
          • (run, config?): void | Promise<void>
          • Called before the runnable starts running, with the Run object.

            Parameters

            Returns void | Promise<void>

    Returns Runnable<RunInput, RunOutput, RunnableConfig>

  • Convenience method for instantiating a RunnableBranch from RunnableLikes (objects, functions, or Runnables).

    Each item in the input except for the last one should be a tuple with two items. The first is a "condition" RunnableLike that returns "true" if the second RunnableLike in the tuple should run.

    The final item in the input should be a RunnableLike that acts as a default branch if no other branches match.

    Type Parameters

    • RunInput = any

    • RunOutput = any

    Parameters

    • branches: [...BranchLike<RunInput, RunOutput>[], RunnableLike<RunInput, RunOutput>]

      An array where the every item except the last is a tuple of [condition, runnable] pairs. The last item is a default runnable which is invoked if no other condition matches.

    Returns RunnableBranch<RunInput, RunOutput>

    A new RunnableBranch.

    Example

    import { RunnableBranch } from "@langchain/core/runnables";

    const branch = RunnableBranch.from([
    [(x: number) => x > 0, (x: number) => x + 1],
    [(x: number) => x < 0, (x: number) => x - 1],
    (x: number) => x
    ]);

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