Development — Adding Custom Node Logic

Step 1: Define Logic

Create a subclass of BaseNodeLogic with async execute() method:

from flet_nodes import BaseNodeLogic

class DoubleLogic(BaseNodeLogic):
    """Multiplies input by 2."""

    async def execute(self, node, **inputs):
        value = inputs.get('value', 0)
        return {'result': value * 2}

Key points: - execute() is async—use await for I/O operations - **inputs contains values from connected ports (or defaults) - Return a dict with output IDs as keys - Raise exceptions to signal errors

Step 2: Register

Register the logic class with a prototype ID:

from flet_nodes import register_node_logic

register_node_logic('math.double', DoubleLogic)

Now users can create nodes with prototype 'math.double' in the UI.

Step 3: Test

Unit Test

import pytest
from flet_nodes import RuntimeNode, InputSocket
from your_module import DoubleLogic

@pytest.mark.asyncio
async def test_double_logic():
    logic = DoubleLogic()
    node = RuntimeNode(id='test', prototype='math.double')

    result = await logic.execute(node, value=5)
    assert result['result'] == 10

Integration Test

Run the example app:

cd examples/flet_nodes_example
uv run --active flet -r src/main.py

Then: 1. Click "Register Types" 2. Click "Demo Nodes" 3. Connect and execute nodes to verify behavior

Tips

• Use node.ui_content to read fallback values from UI controls
• Cache expensive operations if nodes might execute multiple times
• Log execution: Add print() or logging to debug dataflow
• Type hints: Add return type hints for IDE support

Example: Node with UI Input

class InputLogic(BaseNodeLogic):
    async def execute(self, node, **inputs):
        # Read from UI control if no input connected
        if node.ui_content and hasattr(node.ui_content, 'value'):
            value = node.ui_content.value
        else:
            value = inputs.get('fallback', '')

        return {'output': value}