State

LlamaIndex workflows, beyond being event-driven, can also be stateful.

More specifically, the state can be defined as an internal representation of the current workflow execution.

The workflow state is typed, meaning that it can be defined as a type and can be accessed and modified following that type’s property.

Here is an example:

type MyWorkflowState = {
  previous_message: string,
};

You can then add a state to your workflow in this way:

import { createWorkflow } from "@llamaindex/workflow-core";
import { createStatefulMiddleware } from "@llamaindex/workflow-core/middleware/state";

const { withState } = createStatefulMiddleware(
  (state: MyWorkflowState) => state,
);
const workflow = withState(createWorkflow());

And then, in your step handling logic, you can access and modify state properties:

import { workflowEvent } from "@llamaindex/workflow-core";

const startEvent = workflowEvent<{ userInput: string }>();
const stopEvent = workflowEvent<{ result: string }>();

workflow.handle([startEvent], async (context, { data }) => {
  const { sendEvent, state } = context;
  const { userInput } = data;

  const previous_message = state.previous_message;
  state.previous_message = userInput;

  return stopEvent.with({ result: "Processed message: " + userInput + " previous message: " + previous_message });
});

Before running the workflow, remember to initialize the context object with the state:

const { stream, sendEvent } = workflow.createContext({
  previous_message: "my initial previous message",
});

sendEvent(startEvent.with({ userInput: "Hello, how are you?" }));

const result = await stream.until(stopEvent).toArray();
console.log(result[result.length - 1].data);