Installation

Note: Phoenix v1.5 comes with built-in support for LiveView apps. Just create your application with mix phx.new my_app --live. If you are using earlier Phoenix versions or your app already exists, keep on reading.

The instructions below will serve if you are installing the latest stable version from Hex. To start using LiveView, add one of the following dependencies to your mix.exs and run mix deps.get.

If installing from Hex, use the latest version from there:

def deps do
  [
    {:phoenix_live_view, "~> 0.16.3"},
    {:floki, ">= 0.30.0", only: :test}
  ]
end

If you want the latest features, install from GitHub:

def deps do
  [
    {:phoenix_live_view, github: "phoenixframework/phoenix_live_view"},
    {:floki, ">= 0.30.0", only: :test}
  ]

Once installed, update your endpoint's configuration to include a signing salt. You can generate a signing salt by running mix phx.gen.secret 32:

# config/config.exs

config :my_app, MyAppWeb.Endpoint,
   live_view: [signing_salt: "SECRET_SALT"]

Next, add the following imports to your web file in lib/my_app_web.ex:

# lib/my_app_web.ex

def view do
  quote do
    ...
    import Phoenix.LiveView.Helpers
  end
end

def router do
  quote do
    ...
    import Phoenix.LiveView.Router
  end
end

Then add the Phoenix.LiveView.Router.fetch_live_flash/2 plug to your browser pipeline, in place of :fetch_flash:

# lib/my_app_web/router.ex

pipeline :browser do
  ...
  plug :fetch_session
- plug :fetch_flash
+ plug :fetch_live_flash
end

Next, expose a new socket for LiveView updates in your app's endpoint module.

# lib/my_app_web/endpoint.ex

defmodule MyAppWeb.Endpoint do
  use Phoenix.Endpoint

  # ...

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

  # ...
end

Where @session_options are the options given to plug Plug.Session by using a module attribute. If you don't have a @session_options in your endpoint yet, here is how to create one:

Find plug Plug.Session in your endpoint.ex

  plug Plug.Session
    store: :cookie,
    key: "_my_app_key",
    signing_salt: "somesigningsalt"

Move the options to a module attribute at the top of your file:

  @session_options [
    store: :cookie,
    key: "_my_app_key",
    signing_salt: "somesigningsalt"
  ]

Change the plug Plug.Session to use that attribute:

  plug Plug.Session, @session_options

Finally, ensure you have placed a CSRF meta tag inside the <head> tag in your layout (lib/my_app_web/templates/layout/app.html.*) before app.js is included, like so:

<%= csrf_meta_tag() %>
<script defer type="text/javascript" src="<%= Routes.static_path(@conn, "/js/app.js") %>"></script>

and enable connecting to a LiveView socket in your app.js file.

// assets/js/app.js
import {Socket} from "phoenix"
import {LiveSocket} from "phoenix_live_view"

let csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute("content")
let liveSocket = new LiveSocket("/live", Socket, {params: {_csrf_token: csrfToken}})

// Connect if there are any LiveViews on the page
liveSocket.connect()

// Expose liveSocket on window for web console debug logs and latency simulation:
// >> liveSocket.enableDebug()
// >> liveSocket.enableLatencySim(1000)
// The latency simulator is enabled for the duration of the browser session.
// Call disableLatencySim() to disable:
// >> liveSocket.disableLatencySim()
window.liveSocket = liveSocket

The JavaScript above expects phoenix_live_view to be available as a JavaScript dependency. Let's do that.

npm dependencies

If using npm, you need to add LiveView to your assets/package.json. For a regular project, do:

{
  "dependencies": {
    "phoenix": "file:../deps/phoenix",
    "phoenix_html": "file:../deps/phoenix_html",
    "phoenix_live_view": "file:../deps/phoenix_live_view"
  }
}

However, if you're adding phoenix_live_view to an umbrella project, the dependency paths should be modified appropriately:

{
  "dependencies": {
    "phoenix": "file:../../../deps/phoenix",
    "phoenix_html": "file:../../../deps/phoenix_html",
    "phoenix_live_view": "file:../../../deps/phoenix_live_view"
  }
}

Now run the next commands from your web app root:

npm install --prefix assets

If you had previously installed phoenix_live_view and want to get the latest javascript, then force an install with:

npm install --force phoenix_live_view --prefix assets

Layouts

LiveView does not use the default app layout. Instead, you typically call put_root_layout in your router to specify a layout that is used by both "regular" views and live views. In your router, do:

pipeline :browser do
  ...
  plug :put_root_layout, {MyAppWeb.LayoutView, :root}
  ...
end

The layout given to put_root_layout must use <%= @inner_content %> instead of <%= render(@view_module, @view_template, assigns) %>. It is typically very barebones, with mostly <head> and <body> tags. For example:

<!DOCTYPE html>
<html lang="en">
  <head>
    <%= csrf_meta_tag() %>
    <%= live_title_tag assigns[:page_title] || "MyApp" %>
    <link rel="stylesheet" href="<%= Routes.static_path(@conn, "/css/app.css") %>"/>
    <script defer type="text/javascript" src="<%= Routes.static_path(@conn, "/js/app.js") %>"></script>
  </head>
  <body>
    <%= @inner_content %>
  </body>
</html>

Once you have specified a root layout, "app.html.heex" will be rendered within your root layout for all non-LiveViews. You may also optionally define a "live.html.heex" layout to be used across all LiveViews, as we will describe in the next section.

Optionally, you can add a phx-track-static to all script and link elements in your layout that use src and href. This way you can detect when new assets have been deployed by calling static_changed?.

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

phx.gen.live support

While the above instructions are enough to install LiveView in a Phoenix app, if you want to use the phx.gen.live generators that come as part of Phoenix v1.5, you need to do one more change, as those generators assume your application was created with mix phx.new --live.

The change is to define the live_view and live_component functions in your my_app_web.ex file, while refactoring the view function. At the end, they will look like this:

  def view do
    quote do
      use Phoenix.View,
        root: "lib/<%= lib_web_name %>/templates",
        namespace: <%= web_namespace %>

      # Import convenience functions from controllers
      import Phoenix.Controller,
        only: [get_flash: 1, get_flash: 2, view_module: 1, view_template: 1]

      # Include shared imports and aliases for views
      unquote(view_helpers())
    end
  end

  def live_view do
    quote do
      use Phoenix.LiveView,
        layout: {<%= web_namespace %>.LayoutView, "live.html"}

      unquote(view_helpers())
    end
  end

  def live_component do
    quote do
      use Phoenix.LiveComponent

      unquote(view_helpers())
    end
  end

  defp view_helpers do
    quote do
      # Use all HTML functionality (forms, tags, etc)
      use Phoenix.HTML

      # Import LiveView helpers (live_render, live_component, live_patch, etc)
      import Phoenix.LiveView.Helpers

      # Import basic rendering functionality (render, render_layout, etc)
      import Phoenix.View

      import MyAppWeb.ErrorHelpers
      import MyAppWeb.Gettext
      alias MyAppWeb.Router.Helpers, as: Routes
    end
  end

Note that LiveViews are automatically configured to use a "live.html.heex" layout in this line:

use Phoenix.LiveView,
  layout: {<%= web_namespace %>.LayoutView, "live.html"}

"layouts/root.html.heex" is shared by regular and live views, "app.html.heex" is rendered inside the root layout for regular views, and "live.html.heex" is rendered inside the root layout for LiveViews. "live.html.heex" typically starts out as a copy of "app.html.heex", but using the @socket assign instead of @conn. Check the Live Layouts guide for more information.

Progress animation

If you want to show a progress bar as users perform live actions, we recommend using topbar.

You can either add a copy of topbar to assets/vendor/topbar.js or add it as a npm dependency by calling:

$ npm install --prefix assets --save topbar

Then customize LiveView to use it in your assets/js/app.js, right before the liveSocket.connect() call:

import topbar from "topbar"

// Show progress bar on live navigation and form submits
topbar.config({barColors: {0: "#29d"}, shadowColor: "rgba(0, 0, 0, .3)"})
window.addEventListener("phx:page-loading-start", info => topbar.show())
window.addEventListener("phx:page-loading-stop", info => topbar.hide())

Location for LiveView modules

By convention your LiveView modules and heex templates should be placed in lib/my_app_web/live/ directory.

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