how can i pass on parameter i get from the previous node to the next node?

[phoenix-lee-tpe]

i have 3 nodes, node 1 get a parameter from other node then pass on to node 2, now node 3 also needs the same parameter information, how could i pass it from node 2 to node 3?

[dosubot[bot]]

🤖

Hey @phoenix-lee-tpe! Great to see you back in action here. Hope you're doing fantastically well! 🚀

In Langflow, passing a parameter from one node to another in a sequence is done through edges. Each edge represents a connection between two nodes. The source property of an edge represents the id of the node from which the parameter is passed, and the target property represents the id of the node to which the parameter is passed.

Here is an example of how you can create an edge to pass a parameter from node 1 to node 2:

const edge1to2 = {
  id: 'edge-1-2',
  source: 'node-1-id', // replace with your node 1 id
  target: 'node-2-id', // replace with your node 2 id
  animated: true,
  arrowHeadType: 'arrowclosed',
};

And here is how you can create an edge to pass a parameter from node 2 to node 3:

const edge2to3 = {
  id: 'edge-2-3',
  source: 'node-2-id', // replace with your node 2 id
  target: 'node-3-id', // replace with your node 3 id
  animated: true,
  arrowHeadType: 'arrowclosed',
};

After creating these edges, you can add them to your flow using the setEdges function:

setEdges((oldEdges) => [...oldEdges, edge1to2, edge2to3]);

Please note that the actual passing of parameters (i.e., the logic that determines what data is passed from one node to another) is determined by the implementation of your nodes and is not handled directly by the edges or the flow. The edges simply define the connections between nodes. The nodes themselves must be implemented to handle the receipt and transmission of data.

In the Langflow codebase, parameters are passed between nodes through the params attribute of the Vertex class, which is the base class for all types of vertices (nodes) in the graph. This attribute is a dictionary that stores the parameters for each node.

When a node is initialized, the params dictionary is passed to the __init__ method of the Vertex class. In the build method of each node, the params dictionary is used to pass parameters to the _build method, which is responsible for building the node.

For more details, you can refer to the source code of Langflow:

• src/frontend/src/pages/FlowPage/components/PageComponent/index.tsx
• src/backend/langflow/graph/vertex/types.py

I hope this helps! If you have any more questions, feel free to ask.

Best,
Dosu

Sources

• src/frontend/src/pages/FlowPage/components/PageComponent/index.tsx
• src/backend/langflow/graph/vertex/types.py

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