Complex Example

In this more complex example we will be wrapping reactflow a library for building node based applications like flow charts, diagrams, graphs, etc.

Lets start by importing the library reactflow. Lets make a seperate file called reactflow.py and add the following code:

Notice we also use the _get_custom_code method to import the css file that is needed for the styling of the library.

For this tutorial we will wrap three components from Reactflow: ReactFlow, Background, and Controls. Lets start with the ReactFlow component.

Here we will define the tag and the vars that we will need to use the component.

For this tutorial we will define EventHandler props on_nodes_change and on_connect, but you can find all the events that the component triggers in the reactflow docs.

Now lets add the Background and Controls components. We will also create the components using the create method so that we can use them in our app.

Now that we have our components lets build the app.

Lets start by defining the initial nodes and edges that we will use in our app.

Next we will define the state of our app. We have four event handlers: add_random_node, clear_graph, on_connect and on_nodes_change.

The on_nodes_change event handler is triggered when a node is selected and dragged. This function is used to update the position of a node during dragging. It takes a single argument node_changes, which is a list of dictionaries containing various types of metadata. For updating positions, the function specifically processes changes of type position.

Now lets define the UI of our app. We will use the react_flow component and pass in the nodes and edges from our state. We will also add the on_connect event handler to the react_flow component to handle when an edge is connected.

Here is an example of the app running: