How do I change the Enum value using ui?

[kkngsm]

I wanted to create a node that would add values entered from the UI to the Node's input.
/~https://github.com/kkngsm/egui_node_graph/blob/7ed0179666949f66eaa35ee0ce53bb77d590a027/egui_node_graph_example/src/app.rs#L502-L505

So I added AddScalarByUi to MyNodeTemplate
/~https://github.com/kkngsm/egui_node_graph/blob/7ed0179666949f66eaa35ee0ce53bb77d590a027/egui_node_graph_example/src/app.rs#L64-L73

and tried to implement the ui with bottom_ui.
/~https://github.com/kkngsm/egui_node_graph/blob/7ed0179666949f66eaa35ee0ce53bb77d590a027/egui_node_graph_example/src/app.rs#L302-L320

However, I could not change the self in bottom_ui because it is immutable.

How can i achieve my goal?
I hope you will be able to provide the information.

[setzer22]

Hi! @kkngsm

The way the application works is by delaying side effects. In functions such as bottom_ui you should not modify the graph, because it's immutably borrowed. Instead, you add a response to the return value of your function with the necessary information to perform this side effect later on, when you have exclusive access to the graph.

To implement this, you need to create a custom response type that you can return from bottom_ui. To do this, you would need to add a new enum variant to MyResponse. For your particular use case, you probably want to create some sort of AddScalarProperty { id: NodeId } response variant (maybe you need to include additional data in it).

Then, you can apply those side effects once you have mutable access. In the example, this happens here: /~https://github.com/kkngsm/egui_node_graph/blob/7ed0179666949f66eaa35ee0ce53bb77d590a027/egui_node_graph_example/src/app.rs#L381-L393

[kkngsm]

I see! Thank you.