Uses LiveView in the current module to mark it a LiveView.

use Phoenix.LiveView,
  namespace: MyAppWeb,
  container: {:tr, class: "colorized"},
  layout: {MyAppWeb.LayoutView, :app},
  log: :info

options

Options

• :container - configures the container the LiveView will be wrapped in

• :global_prefixes - the global prefixes to use for components. See Global Attributes in Phoenix.Component for more information.

• :layout - configures the layout the LiveView will be rendered in. This layout can be overridden by on mount/3 or via the :layout option in Phoenix.LiveView.Router.live_session/2

• :log - configures the log level for the LiveView

• :namespace - configures the namespace the LiveView is in

Allows an upload for the provided name.

options

Options

• :accept - Required. A list of unique file type specifiers or the atom :any to allow any kind of file. For example, [".jpeg"], :any, etc.

• :max_entries - The maximum number of selected files to allow per file input. Defaults to 1.

• :max_file_size - The maximum file size in bytes to allow to be uploaded. Defaults 8MB. For example, 12_000_000.

• :chunk_size - The chunk size in bytes to send when uploading. Defaults 64_000.

• :chunk_timeout - The time in milliseconds to wait before closing the upload channel when a new chunk has not been received. Defaults 10_000.

• :external - The 2-arity function for generating metadata for external client uploaders. See the Uploads section for example usage.

• :progress - The optional 3-arity function for receiving progress events

• :auto_upload - Instructs the client to upload the file automatically on file selection instead of waiting for form submits. Default false.

Raises when a previously allowed upload under the same name is still active.

examples

Examples

allow_upload(socket, :avatar, accept: ~w(.jpg .jpeg), max_entries: 2)
allow_upload(socket, :avatar, accept: :any)

For consuming files automatically as they are uploaded, you can pair auto_upload: true with a custom progress function to consume the entries as they are completed. For example:

allow_upload(socket, :avatar, accept: :any, progress: &handle_progress/3, auto_upload: true)

defp handle_progress(:avatar, entry, socket) do
  if entry.done? do
    uploaded_file =
      consume_uploaded_entry(socket, entry, fn %{} = meta ->
        {:ok, ...}
      end)

    {:noreply, put_flash(socket, :info, "file #{uploaded_file.name} uploaded")}
  else
    {:noreply, socket}
  end
end

Attaches the given fun by name for the lifecycle stage into socket.

Note: This function is for server-side lifecycle callbacks. For client-side hooks, see the JS Interop guide.

Hooks provide a mechanism to tap into key stages of the LiveView lifecycle in order to bind/update assigns, intercept events, patches, and regular messages when necessary, and to inject common functionality. Use attach_hook/1 on any of the following lifecycle stages: :handle_params, :handle_event, :handle_info, and :after_render. To attach a hook to the :mount stage, use on_mount/1.

Note: only :after_render hooks are currently supported in LiveComponents.

return-values

Return Values

Lifecycle hooks take place immediately before a given lifecycle callback is invoked on the LiveView. With the exception of :after_render, a hook may return {:halt, socket} to halt the reduction, otherwise it must return {:cont, socket} so the operation may continue until all hooks have been invoked for the current stage.

For :after_render hooks, the socket itself must be returned. Any updates to the socket assigns will not trigger a new render or diff calculation to the client.

halting-the-lifecycle

Halting the lifecycle

Note that halting from a hook will halt the entire lifecycle stage. This means that when a hook returns {:halt, socket} then the LiveView callback will not be invoked. This has some implications.

implications-for-plugin-authors

Implications for plugin authors

When defining a plugin that matches on specific callbacks, you must define a catch-all clause, as your hook will be invoked even for events you may not be interested on.

implications-for-end-users

Implications for end-users

Allowing a hook to halt the invocation of the callback means that you can attach hooks to intercept specific events before detaching themselves, while allowing other events to continue normally.

replying-to-events

Replying to events

Hooks attached to the :handle_event stage are able to reply to client events by returning {:halt, reply, socket}. This is useful especially for JavaScript interoperability because a client hook can push an event and receive a reply.

examples

Examples

Attaching and detaching a hook:

def mount(_params, _session, socket) do
  socket =
    attach_hook(socket, :my_hook, :handle_event, fn
      "very-special-event", _params, socket ->
        # Handle the very special event and then detach the hook
        {:halt, detach_hook(socket, :my_hook, :handle_event)}

      _event, _params, socket ->
        {:cont, socket}
    end)

  {:ok, socket}
end

Replying to a client event:

# JavaScript:
# let Hooks = {}
# Hooks.ClientHook = {
#   mounted() {
#     this.pushEvent("ClientHook:mounted", {hello: "world"}, (reply) => {
#       console.log("received reply:", reply)
#     })
#   }
# }
# let liveSocket = new LiveSocket("/live", Socket, {hooks: Hooks, ...})

def render(assigns) do
  ~H"""
  <div id="my-client-hook" phx-hook="ClientHook"></div>
  """
end

def mount(_params, _session, socket) do
  socket =
    attach_hook(socket, :reply_on_client_hook_mounted, :handle_event, fn
      "ClientHook:mounted", params, socket ->
        {:halt, params, socket}

      _, _, socket ->
        {:cont, socket}
    end)

  {:ok, socket}
end

Cancels an upload for the given entry.

examples

Examples

<%= for entry <- @uploads.avatar.entries do %>
  ...
  <button phx-click="cancel-upload" phx-value-ref="<%= entry.ref %>">cancel</button>
<% end %>

def handle_event("cancel-upload", %{"ref" => ref}, socket) do
  {:noreply, cancel_upload(socket, :avatar, ref)}
end

Clears the flash.

examples

Examples

iex> clear_flash(socket)

Clears a key from the flash.

examples

Examples

iex> clear_flash(socket, :info)

Returns true if the socket is connected.

Useful for checking the connectivity status when mounting the view. For example, on initial page render, the view is mounted statically, rendered, and the HTML is sent to the client. Once the client connects to the server, a LiveView is then spawned and mounted statefully within a process. Use connected?/1 to conditionally perform stateful work, such as subscribing to pubsub topics, sending messages, etc.

examples

Examples

defmodule DemoWeb.ClockLive do
  use Phoenix.LiveView
  ...
  def mount(_params, _session, socket) do
    if connected?(socket), do: :timer.send_interval(1000, self(), :tick)

    {:ok, assign(socket, date: :calendar.local_time())}
  end

  def handle_info(:tick, socket) do
    {:noreply, assign(socket, date: :calendar.local_time())}
  end
end

Consumes the uploaded entries.

Raises when there are still entries in progress. Typically called when submitting a form to handle the uploaded entries alongside the form data. For form submissions, it is guaranteed that all entries have completed before the submit event is invoked. Once entries are consumed, they are removed from the upload.

The function passed to consume may return a tagged tuple of the form {:ok, my_result} to collect results about the consumed entries, or {:postpone, my_result} to collect results, but postpone the file consumption to be performed later.

examples

Examples

def handle_event("save", _params, socket) do
  uploaded_files =
    consume_uploaded_entries(socket, :avatar, fn %{path: path}, _entry ->
      dest = Path.join("priv/static/uploads", Path.basename(path))
      File.cp!(path, dest)
      {:ok, Routes.static_path(socket, "/uploads/#{Path.basename(dest)}")}
    end)
  {:noreply, update(socket, :uploaded_files, &(&1 ++ uploaded_files))}
end

Consumes an individual uploaded entry.

Raises when the entry is still in progress. Typically called when submitting a form to handle the uploaded entries alongside the form data. Once entries are consumed, they are removed from the upload.

This is a lower-level feature than consume_uploaded_entries/3 and useful for scenarios where you want to consume entries as they are individually completed.

Like consume_uploaded_entries/3, the function passed to consume may return a tagged tuple of the form {:ok, my_result} to collect results about the consumed entries, or {:postpone, my_result} to collect results, but postpone the file consumption to be performed later.

examples

Examples

def handle_event("save", _params, socket) do
  case uploaded_entries(socket, :avatar) do
    {[_|_] = entries, []} ->
      uploaded_files = for entry <- entries do
        consume_uploaded_entry(socket, entry, fn %{path: path} ->
          dest = Path.join("priv/static/uploads", Path.basename(path))
          File.cp!(path, dest)
          {:ok, Routes.static_path(socket, "/uploads/#{Path.basename(dest)}")}
        end)
      end
      {:noreply, update(socket, :uploaded_files, &(&1 ++ uploaded_files))}

    _ ->
      {:noreply, socket}
  end
end

Detaches a hook with the given name from the lifecycle stage.

Note: This function is for server-side lifecycle callbacks. For client-side hooks, see the JS Interop guide.

If no hook is found, this function is a no-op.

examples

Examples

def handle_event(_, socket) do
  {:noreply, detach_hook(socket, :hook_that_was_attached, :handle_event)}
end

Revokes a previously allowed upload from allow_upload/3.

examples

Examples

disallow_upload(socket, :avatar)

Accesses a given connect info key from the socket.

The following keys are supported: :peer_data, :trace_context_headers, :x_headers, :uri, and :user_agent.

The connect information is available only during mount. During disconnected render, all keys are available. On connected render, only the keys explicitly declared in your socket are available. See Phoenix.Endpoint.socket/3 for a complete description of the keys.

examples

Examples

The first step is to declare the connect_info you want to receive. Typically, it includes at least the session, but you must include all other keys you want to access on connected mount, such as :peer_data:

socket "/live", Phoenix.LiveView.Socket,
  websocket: [connect_info: [:peer_data, session: @session_options]]

Those values can now be accessed on the connected mount as get_connect_info/2:

def mount(_params, _session, socket) do
  peer_data = get_connect_info(socket, :peer_data)
  {:ok, assign(socket, ip: peer_data.address)}
end

If the key is not available, usually because it was not specified in connect_info, it returns nil.

Accesses the connect params sent by the client for use on connected mount.

Connect params are only sent when the client connects to the server and only remain available during mount. nil is returned when called in a disconnected state and a RuntimeError is raised if called after mount.

reserved-params

Reserved params

The following params have special meaning in LiveView:

• "_csrf_token" - the CSRF Token which must be explicitly set by the user when connecting
• "_mounts" - the number of times the current LiveView is mounted. It is 0 on first mount, then increases on each reconnect. It resets when navigating away from the current LiveView or on errors
• "_track_static" - set automatically with a list of all href/src from tags with the phx-track-static annotation in them. If there are no such tags, nothing is sent
• "_live_referer" - sent by the client as the referer URL when a live navigation has occurred from push_navigate or client link navigate.

examples

Examples

def mount(_params, _session, socket) do
  {:ok, assign(socket, width: get_connect_params(socket)["width"] || @width)}
end

Declares a module callback to be invoked on the LiveView's mount.

The function within the given module, which must be named on_mount, will be invoked before both disconnected and connected mounts. The hook has the option to either halt or continue the mounting process as usual. If you wish to redirect the LiveView, you must halt, otherwise an error will be raised.

Tip: if you need to define multiple on_mount callbacks, avoid defining multiple modules. Instead, pass a tuple and use pattern matching to handle different cases:

def on_mount(:admin, _params, _session, socket) do
  {:cont, socket}
end

def on_mount(:user, _params, _session, socket) do
  {:cont, socket}
end

And then invoke it as:

on_mount {MyAppWeb.SomeHook, :admin}
on_mount {MyAppWeb.SomeHook, :user}

Registering on_mount hooks can be useful to perform authentication as well as add custom behaviour to other callbacks via attach_hook/4.

examples

Examples

The following is an example of attaching a hook via Phoenix.LiveView.Router.live_session/3:

# lib/my_app_web/live/init_assigns.ex
defmodule MyAppWeb.InitAssigns do
  @moduledoc """
  Ensures common `assigns` are applied to all LiveViews attaching this hook.
  """
  import Phoenix.LiveView
  import Phoenix.Component

  def on_mount(:default, _params, _session, socket) do
    {:cont, assign(socket, :page_title, "DemoWeb")}
  end

  def on_mount(:user, params, session, socket) do
    # code
  end

  def on_mount(:admin, params, session, socket) do
    # code
  end
end

# lib/my_app_web/router.ex
defmodule MyAppWeb.Router do
  use MyAppWeb, :router

  # pipelines, plugs, etc.

  live_session :default, on_mount: MyAppWeb.InitAssigns do
    scope "/", MyAppWeb do
      pipe_through :browser
      live "/", PageLive, :index
    end
  end

  live_session :authenticated, on_mount: {MyAppWeb.InitAssigns, :user} do
    scope "/", MyAppWeb do
      pipe_through [:browser, :require_user]
      live "/profile", UserLive.Profile, :index
    end
  end

  live_session :admins, on_mount: {MyAppWeb.InitAssigns, :admin} do
    scope "/admin", MyAppWeb.Admin do
      pipe_through [:browser, :require_user, :require_admin]
      live "/", AdminLive.Index, :index
    end
  end
end

Pushes an event to the client.

Events can be handled in two ways:

1. They can be handled on window via addEventListener. A "phx:" prefix will be added to the event name.

2. They can be handled inside a hook via handleEvent.

Note that events are dispatched to all active hooks on the client who are handling the given event. If you need to scope events, then this must be done by namespacing them.

hook-example

Hook example

If you push a "scores" event from your LiveView:

{:noreply, push_event(socket, "scores", %{points: 100, user: "josé"})}

A hook declared via phx-hook can handle it via handleEvent:

this.handleEvent("scores", data => ...)

window-example

window example

All events are also dispatched on the window. This means you can handle them by adding listeners. For example, if you want to remove an element from the page, you can do this:

{:noreply, push_event(socket, "remove-el", %{id: "foo-bar"})}

And now in your app.js you can register and handle it:

window.addEventListener(
  "phx:remove-el",
  e => document.getElementById(e.detail.id).remove()
)

Annotates the socket for navigation to another LiveView.

The current LiveView will be shutdown and a new one will be mounted in its place, without reloading the whole page. This can also be used to remount the same LiveView, in case you want to start fresh. If you want to navigate to the same LiveView without remounting it, use push_patch/2 instead.

options

Options

• :to - the required path to link to. It must always be a local path
• :replace - the flag to replace the current history or push a new state. Defaults false.

examples

Examples

{:noreply, push_navigate(socket, to: "/")}
{:noreply, push_navigate(socket, to: "/", replace: true)}

Annotates the socket for navigation within the current LiveView.

When navigating to the current LiveView, handle_params/3 is immediately invoked to handle the change of params and URL state. Then the new state is pushed to the client, without reloading the whole page while also maintaining the current scroll position. For live navigation to another LiveView, use push_navigate/2.

options

Options

• :to - the required path to link to. It must always be a local path
• :replace - the flag to replace the current history or push a new state. Defaults false.

examples

Examples

{:noreply, push_patch(socket, to: "/")}
{:noreply, push_patch(socket, to: "/", replace: true)}

Annotates the socket for navigation to another LiveView.

The current LiveView will be shutdown and a new one will be mounted in its place, without reloading the whole page. This can also be used to remount the same LiveView, in case you want to start fresh. If you want to navigate to the same LiveView without remounting it, use push_patch/2 instead.

options

Options

• :to - the required path to link to. It must always be a local path
• :replace - the flag to replace the current history or push a new state. Defaults false.

examples

Examples

{:noreply, push_redirect(socket, to: "/")}
{:noreply, push_redirect(socket, to: "/", replace: true)}

Adds a flash message to the socket to be displayed.

Note: While you can use put_flash/3 inside a Phoenix.LiveComponent, components have their own @flash assigns. The @flash assign in a component is only copied to its parent LiveView if the component calls push_navigate/2 or push_patch/2.

Note: You must also place the Phoenix.LiveView.Router.fetch_live_flash/2 plug in your browser's pipeline in place of fetch_flash for LiveView flash messages be supported, for example:

import Phoenix.LiveView.Router

pipeline :browser do
  ...
  plug :fetch_live_flash
end

examples

Examples

iex> put_flash(socket, :info, "It worked!")
iex> put_flash(socket, :error, "You can't access that page")

Annotates the socket for redirect to a destination path.

Note: LiveView redirects rely on instructing client to perform a window.location update on the provided redirect location. The whole page will be reloaded and all state will be discarded.

options

Options

• :to - the path to redirect to. It must always be a local path
• :external - an external path to redirect to. Either a string or {scheme, url} to redirect to a custom scheme

Asynchronously updates a Phoenix.LiveComponent with new assigns.

The :id that identifies the component must be passed as part of the assigns and it will be used to identify the live components to be updated.

The pid argument is optional and it defaults to the current process, which means the update instruction will be sent to a component running on the same LiveView. If the current process is not a LiveView or you want to send updates to a live component running on another LiveView, you should explicitly pass the LiveView's pid instead.

When the component receives the update, first the optional preload/1 then update/2 is invoked with the new assigns. If update/2 is not defined all assigns are simply merged into the socket. The assigns received as the first argument of the update/2 callback will only include the new assigns passed from this function. Pre-existing assigns may be found in socket.assigns.

While a component may always be updated from the parent by updating some parent assigns which will re-render the child, thus invoking update/2 on the child component, send_update/3 is useful for updating a component that entirely manages its own state, as well as messaging between components mounted in the same LiveView.

examples

Examples

def handle_event("cancel-order", _, socket) do
  ...
  send_update(Cart, id: "cart", status: "cancelled")
  {:noreply, socket}
end

def handle_event("cancel-order-asynchronously", _, socket) do
  ...
  pid = self()

  Task.start(fn ->
    # Do something asynchronously
    send_update(pid, Cart, id: "cart", status: "cancelled")
  end)

  {:noreply, socket}
end

Similar to send_update/3 but the update will be delayed according to the given time_in_milliseconds.

examples

Examples

def handle_event("cancel-order", _, socket) do
  ...
  send_update_after(Cart, [id: "cart", status: "cancelled"], 3000)
  {:noreply, socket}
end

def handle_event("cancel-order-asynchronously", _, socket) do
  ...
  pid = self()

  Task.start(fn ->
    # Do something asynchronously
    send_update_after(pid, Cart, [id: "cart", status: "cancelled"], 3000)
  end)

  {:noreply, socket}
end

Returns true if the socket is connected and the tracked static assets have changed.

This function is useful to detect if the client is running on an outdated version of the marked static files. It works by comparing the static paths sent by the client with the one on the server.

Note: this functionality requires Phoenix v1.5.2 or later.

To use this functionality, the first step is to annotate which static files you want to be tracked by LiveView, with the phx-track-static. For example:

<link phx-track-static rel="stylesheet" href="<%= Routes.static_path(@conn, "/css/app.css") %>"/>
<script defer phx-track-static type="text/javascript" src="<%= Routes.static_path(@conn, "/js/app.js") %>"></script>

Now, whenever LiveView connects to the server, it will send a copy src or href attributes of all tracked statics and compare those values with the latest entries computed by mix phx.digest in the server.

The tracked statics on the client will match the ones on the server the huge majority of times. However, if there is a new deployment, those values may differ. You can use this function to detect those cases and show a banner to the user, asking them to reload the page. To do so, first set the assign on mount:

def mount(params, session, socket) do
  {:ok, assign(socket, static_changed?: static_changed?(socket))}
end

And then in your views:

<%= if @static_changed? do %>
  <div id="reload-static">
    The app has been updated. Click here to <a href="#" onclick="window.location.reload()">reload</a>.
  </div>
<% end %>

If you prefer, you can also send a JavaScript script that immediately reloads the page.

Note: only set phx-track-static on your own assets. For example, do not set it in external JavaScript files:

<script defer phx-track-static type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>

Because you don't actually serve the file above, LiveView will interpret the static above as missing, and this function will return true.

Assigns a new stream to the socket.

Streams are a mechanism for managing large collections on the client without keeping the resources on the server.

• name - The string or atom name of the key to place under the @streams assign.
• items - The enumerable of items for initial insert

The following options are supported:

• :dom_id - The optional function to generate each stream item's DOM id. The function accepts each stream item and converts the item to a string id. By default, the :id field of a map or struct will be used if the item has such a field, and will be prefixed by the name hyphenated with the id. For example, the following definitions are equivalent:

  stream(socket, :songs, songs)
  stream(socket, :songs, songs, dom_id: &("songs-#{&1.id}"))

Once a stream is defined, a new @streams assign is available containing the name of the defined streams. For example, in the above definition, the stream may be referenced as @streams.songs in your template. Stream items are temporary and freed from socket state as soon as they are rendered.

required-dom-attributes

Required DOM attributes

For stream items to be trackable on the client, the following requirements must be met:

1. The parent DOM container must include a phx-update="stream" attribute, along with a unique DOM id.
2. Each stream item must include its DOM id on the item's element.

When consuming a stream in a template, the DOM id and item is passed as a tuple, allowing convenient inclusion of the DOM id for each item. For example:

<table>
  <tbody id="songs" phx-update="stream">
    <tr
      :for={{dom_id, song} <- @streams.songs}
      id={dom_id}
    >
      <td><%= song.title %></td>
      <td><%= song.duration %></td>
    </tr>
  </tbody>
</table>

We consume the stream in a for comprehension by referencing the @streams.songs assign. We used the computed DOM id to populate the <tr> id, then we render the table row as usual.

Now stream_insert/3 and stream_delete/3 may be issued and new rows will be inserted or deleted from the client.

Deletes an item from the stream.

The item's DOM is computed from the :dom_id provided in the stream/3 definition. Delete information for this DOM id is sent to the client and the item's element is removed from the DOM, following the same behavior of element removal, such as invoking phx-remove commands and executing client hook destroyed() callbacks.

examples

Examples

def handle_event("delete", %{"id" => id})
  song = get_song!(id)
  {:noreply, stream_delete(socket, :songs, song)}
end

See stream_delete_by_dom_id/3 to remove an item without requiring the original datastructure.

Deletes an item from the stream given its computed DOM id.

Behaves just like stream_delete/3, but accept the precomputed DOM id, which allows deleting from a stream without fetching or building the original stream datastructure.

examples

Examples

def render(assigns) do
  ~H"""
  <table>
    <tbody id="songs" phx-update="stream">
      <tr
        :for={{dom_id, song} <- @streams.songs}
        id={dom_id}
      >
        <td><%= song.title %></td>
        <td><button phx-click={JS.push("delete", value: %{id: dom_id})}>delete</button></td>
      </tr>
    </tbody>
  </table>
  """
end

def handle_event("delete", %{"id" => dom_id})
  {:noreply, stream_delete_by_dom_id(socket, :songs, dom_id)}
end

Inserts a new item or updates an existing item in the stream.

By default, the item is appended to the parent DOM container. The :at option may be provided to insert or update an item to a particular index in the collection on the client.

examples

Examples

Imagine you define a stream on mount with a single item:

stream(socket, :songs, [%Song{id: 1, title: "Song 1"}])

Then, in a callback such as handle_info or handle_event, you can append a new song:

stream_insert(socket, :songs, %Song{id: 2, title: "Song 2"})

Or prepend a new song with at: 0:

stream_insert(socket, :songs, %Song{id: 2, title: "Song 2"}, at: 0)

Or updating an existing song, while also moving it to the top of the collection:

stream_insert(socket, :songs, %Song{id: 1, title: "Song 1 updated"}, at: 0)

updating-items

Updating Items

As shown, an existing item on the client can be updated by issuing a stream_insert for the existing item. When the client updates an existing item with an "append" operation (passing the at: -1 option), the item will remain in the same location as it was previously, and will not be moved to the end of the parent children. To both update an existing item and move it to the end of a collection, issue a stream_delete, followed by a stream_insert. For example:

song = get_song!(id)

socket
|> stream_delete(:songs, song)
|> stream_insert(:songs, song, at: -1)

See stream_delete/3 for more information on deleting items.

Returns the transport pid of the socket.

Raises ArgumentError if the socket is not connected.

examples

Examples

iex> transport_pid(socket)
#PID<0.107.0>

Returns the completed and in progress entries for the upload.

examples

Examples

case uploaded_entries(socket, :photos) do
  {[_ | _] = completed, []} ->
    # all entries are completed

  {[], [_ | _] = in_progress} ->
    # all entries are still in progress
end