Nested workflow vs just a field in Workflow class

[InAnYan]

You have a dedicated page for nested workflows: https://docs.llamaindex.ai/en/stable/understanding/workflows/nested/.

Nested workflows currently work like this:

1. You specify them in start action as a parameter:

class MainWorkflow(Workflow):
    @step
    async def start(
        self, ctx: Context, ev: StartEvent, reflection_workflow: Workflow
    ) -> Step2Event: ...

2. And then, when you use the workflow, you should call add_workflow:

w = MainWorkflow(timeout=10, verbose=False)
w.add_workflows(reflection_workflow=...)

Why would I do all of this, instead of just creating a field in my workflow class?:

class MainWorkflow(Workflow):
	reflection_workflow: Workflow
	
	def __init__(reflection_workflow: Workflow):
		self.reflection_workflow = reflection_workflow

    @step
    async def start(
        self, ctx: Context, ev: StartEvent
    ) -> Step2Event: ...

[dosubot[bot]]

Hey @InAnYan, I'm here to help you out with any bugs, questions, or contributions you have in mind. Let's figure this out together!

Using nested workflows in LlamaIndex offers several advantages over simply creating a field in your workflow class:

1. Modularity and Flexibility: Nested workflows allow you to insert entire workflows into specific slots within an existing workflow. This modular approach enables you to easily modify or replace parts of a workflow without altering the entire structure. For example, you can customize specific steps by supplying different workflows as needed ^[1].

2. Reusability: By using nested workflows, you can create reusable components that can be plugged into different workflows. This promotes code reuse and reduces duplication ^[1].

3. Customization: Users can provide custom workflows for specific steps, allowing for tailored behavior while maintaining a consistent overall workflow structure. This is particularly useful when different users or scenarios require different processing logic ^[1].

4. Default Workflows: The method supports the use of default workflows, which can be set for slots that might not always require customization. This provides a good "out of the box" experience for users who may not want to customize every aspect of the workflow ^[1].

Overall, nested workflows provide a more dynamic and flexible way to manage complex workflows compared to using fields in the workflow class.

To continue talking to Dosu, mention @dosu.

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[YutackPark]

I also have the same confusion. Could not understand why extra complication (.add_workflow method) is introduced. It should have some advantage over using workflow as a field