Handlers

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="<%= struct.id %>"


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

handle_params

• 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}
end

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

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

handle_event

• 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}
end 

handle_info

• 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}
end