We have a simple case where a form has two dropdowns. The options in the second rely on the choice of the first.

In rails, our go-to pattern for this was as follows:

• Create the template to render whatever the default state of the dropdowns is.
• Create an action that returns just the options tags for the submitted choice.
• Using JS, when the first selection box is changed, make an ajax call to that new action. On response, swap out the old DOM element containing the old options with the new options.

At first, I thought LiveView was the go to on this, but after looking at LiveView, it seems like the entirety of the app needs to be written as a LiveView app. This is not, and it’s already pretty massive. Too massive to make the adjustment.

Then, I thought Channels might be the answer, but it looks like channels is a way to talk server → client.

So, how are people doing this daily in the Phoenix world?

Thanks!