A button that populates a form field

I have a form backed by a changeset like mentioned here Form bindings β€” Phoenix LiveView v0.15.7
Say I want a button <button phx-click="foo">Foo</button> that will populate email with some value. Problem is I do not want this button to submit the form. Hence params will not contain the form data and without the form data I cannot create new changeset and update socket with it like the other handlers for save or validate

def handle_event("foo", params, socket) do
    IO.inspect(params) #%{"value" => ""}
    {:noreply, socket}

Any ideas how I can do this?

You can use a phx-change handler to save the part you need later in your socket assigns, when the user press the foo button you can then use those info in your foo handler.

If you don’t want the button to submit the form, be sure to add type="button" to replace the default type of "submit".


Also just to give an example for the solution derek mentioned above:

Assuming you have validation for your form similar to this

def handle_event("validate", %{"user" => params}, socket) do
  changeset =
    |> Users.change_user(params)
    |> Map.put(:action, :insert)

  {:noreply, assign(socket, changeset: changeset)}

then there should be an up-to-date changeset within the socket assigns. Therefore you can use the changeset assign in your handle_event/3

def handle_event("foo", params, socket) do
  new_changeset = socket.assigns.changeset |> some_functions

  {:noreply, assign(socket, changeset: new_changeset)}
1 Like

Thank guys. I am having a :man_facepalming: moment right now.