Pantrypoints Pantrypoints


January 22, 2022 2 minutes  • 229 words
Table of contents

Handlers handle events from the HTML attributes phx- in the view and render the changes in the data (or “state”) by updating the assign-map in the socket-struct.

phx-value-id="<%= %>"

%{"input-data" => elixir-variable-repersenting-a-string}


  • handles URL parameters that affect Routes via live_patch
  • why not call it as handle_url??
  • sends an event as data-phx-link-state
  • always invoked after mount
  • handles dynamic states, just as mount handles static states
handle_params(parameters_of_url, url, socket) do 
  # manipulate the socket data here to automatically output and update the view
  {:noreply, socket}
# has parameters
def handle_params(%{"id" => id}, parameters_of_url, url, socket) do 
  # manipulate the socket data via the id state
  {:noreply, socket}

# empty parameters
def handle_params(%{_, _url, socket) do
  # if no url parameter is entered then just show the socket
  {:noreply, socket}

# rendering whatever
def render(data) do
  always_needed_assigns = %{key: data}
    <%= @key %>


  • handles external messages (events) from the template bindings such as phx-click
  • why not call it handle_external???
  • must return :no_reply tuple {:no_reply, socket}
def handle_event("name_of_external_message_or_event_in_html", %{metadata_about_the_event}, socket_struct) do
  # set the value
  key = socket.assigns.key + 10
  socket = assign(socket, key: value)

  # update the value
  socket = update(socket, :key, &(&1 + 10))

  {:no_reply, socket}


  • handles internal messages (info)
  • why not call it handle_internal???
  • must return :no_reply tuple {:no_reply, socket}
def handle_info(name_of_internal_message, socket_struct) do
  assign(socket, :key, value)
  {:no_reply, socket}
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