defmodule Phoenix.LiveView do
@moduledoc ~S'''
LiveView provides rich, real-time user experiences with
server-rendered HTML.
The LiveView programming model is declarative: instead of
saying "once event X happens, change Y on the page",
events in LiveView are regular messages which may cause
changes to its state. Once the state changes, LiveView will
re-render the relevant parts of its HTML template and push it
to the browser, which updates itself in the most efficient
manner. This means developers write LiveView templates as
any other server-rendered HTML and LiveView does the hard
work of tracking changes and sending the relevant diffs to
the browser.
A LiveView is just a process that receives events as messages and updates
its state. The state itself is nothing more than functional and immutable
Elixir data structures. The events are either internal application messages
(usually emitted by `Phoenix.PubSub`) or sent by the client/browser.
LiveView is first rendered statically as part of regular
HTTP requests, which provides quick times for "First Meaningful
Paint", in addition to helping search and indexing engines.
Then a persistent connection is established between client and
server. This allows LiveView applications to react faster to user
events as there is less work to be done and less data to be sent
compared to stateless requests that have to authenticate, decode, load,
and encode data on every request. The flipside is that LiveView
uses more memory on the server compared to stateless requests.
## Life-cycle
A LiveView begins as a regular HTTP request and HTML response,
and then upgrades to a stateful view on client connect,
guaranteeing a regular HTML page even if JavaScript is disabled.
Any time a stateful view changes or updates its socket assigns, it is
automatically re-rendered and the updates are pushed to the client.
You begin by rendering a LiveView typically from your router.
When LiveView is first rendered, the `c:mount/3` callback is invoked
with the current params, the current session and the LiveView socket.
As in a regular request, `params` contains public data that can be
modified by the user. The `session` always contains private data set
by the application itself. The `c:mount/3` callback wires up socket
assigns necessary for rendering the view. After mounting, `c:handle_params/3`
is invoked so uri and query params are handled. Finally, `c:render/1`
is invoked and the HTML is sent as a regular HTML response to the
client.
After rendering the static page, LiveView connects from the client
to the server where stateful views are spawned to push rendered updates
to the browser, and receive client events via `phx-` bindings. Just like
the first rendering, `c:mount/3`, is invoked with params, session,
and socket state. However in the connected client case, a LiveView process
is spawned on the server, runs `c:handle_params/3` again and then pushes
the result of `c:render/1` to the client and continues on for the duration
of the connection. If at any point during the stateful life-cycle a crash
is encountered, or the client connection drops, the client gracefully
reconnects to the server, calling `c:mount/3` and `c:handle_params/3` again.
LiveView also allows attaching hooks to specific life-cycle stages with
`attach_hook/4`.
## Example
Before writing your first example, make sure that Phoenix LiveView
is properly installed. All applications generated with Phoenix v1.6
and later come with LiveView installed and configured. For previously
existing projects, please follow the steps in the
[installation guide](installation.md) before continuing.
A LiveView is a simple module that requires two callbacks: `c:mount/3`
and `c:render/1`:
defmodule MyAppWeb.ThermostatLive do
# In Phoenix v1.6+ apps, the line below should be: use MyAppWeb, :live_view
use Phoenix.LiveView
def render(assigns) do
~H"""
Current temperature: <%= @temperature %>
"""
end
def mount(_params, %{"current_user_id" => user_id}, socket) do
temperature = Thermostat.get_user_reading(user_id)
{:ok, assign(socket, :temperature, temperature)}
end
end
The `c:render/1` callback receives the `socket.assigns` and is responsible
for returning rendered content. We use the `~H` sigil to define a HEEx
template, which stands for HTML+EEx. They are an extension of Elixir's
builtin EEx templates, with support for HTML validation, syntax-based
components, smart change tracking, and more. You can learn more about
the template syntax in `Phoenix.Component.sigil_H/2` (note
`Phoenix.Component` is automatically imported when you use `Phoenix.LiveView`).
Next, decide where you want to use your LiveView.
You can serve the LiveView directly from your router (recommended):
defmodule MyAppWeb.Router do
use Phoenix.Router
import Phoenix.LiveView.Router
scope "/", MyAppWeb do
live "/thermostat", ThermostatLive
end
end
*Note:* the above assumes there is `plug :put_root_layout` call
in your router that configures the LiveView layout. This call is
automatically included in Phoenix v1.6 apps and described in
[the installation guide](installation.md#layouts).
Alternatively, you can `live_render` from any template. In your view:
import Phoenix.Component
Then in your template:
<h1>Temperature Control</h1>
<%= live_render(@conn, MyAppWeb.ThermostatLive) %>
Once the LiveView is rendered, a regular HTML response is sent. In your
app.js file, you should find the following:
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}})
liveSocket.connect()
After the client connects, `c:mount/3` will be invoked inside a spawned
LiveView process. At this point, you can use `connected?/1` to
conditionally perform stateful work, such as subscribing to pubsub topics,
sending messages, etc. For example, you can periodically update a LiveView
with a timer:
defmodule DemoWeb.ThermostatLive do
use Phoenix.LiveView
...
def mount(_params, %{"current_user_id" => user_id}, socket) do
if connected?(socket), do: Process.send_after(self(), :update, 30000)
case Thermostat.get_user_reading(user_id) do
{:ok, temperature} ->
{:ok, assign(socket, temperature: temperature, user_id: user_id)}
{:error, _reason} ->
{:ok, redirect(socket, to: "/error")}
end
end
def handle_info(:update, socket) do
Process.send_after(self(), :update, 30000)
{:ok, temperature} = Thermostat.get_reading(socket.assigns.user_id)
{:noreply, assign(socket, :temperature, temperature)}
end
end
We used `connected?(socket)` on mount to send our view a message every 30s if
the socket is in a connected state. We receive the `:update` message in the
`c:handle_info/2` callback, just like in an Elixir `GenServer`, and update our
socket assigns. Whenever a socket's assigns change, `c:render/1` is automatically
invoked, and the updates are sent to the client.
## Colocating templates
In the examples above, we have placed the template directly inside the
LiveView:
defmodule MyAppWeb.ThermostatLive do
use Phoenix.LiveView
def render(assigns) do
~H"""
Current temperature: <%= @temperature %>
"""
end
For larger templates, you can place them in a file in the same directory
and same name as the LiveView. For example, if the file above is placed
at `lib/my_app_web/live/thermostat_live.ex`, you can also remove the
`c:render/1` definition above and instead put the template code at
`lib/my_app_web/live/thermostat_live.html.heex`.
In all cases, each assign in the template will be accessible as `@assign`.
You can learn more about [assigns and HEEx templates in their own guide](assigns-eex.md).
## Bindings
Phoenix supports DOM element bindings for client-server interaction. For
example, to react to a click on a button, you would render the element:
<button phx-click="inc_temperature">+</button>
Then on the server, all LiveView bindings are handled with the `c:handle_event/3`
callback, for example:
def handle_event("inc_temperature", _value, socket) do
{:ok, new_temp} = Thermostat.inc_temperature(socket.assigns.id)
{:noreply, assign(socket, :temperature, new_temp)}
end
To update UI state, for example, to open and close dropdowns, switch tabs,
etc, LiveView also supports JS commands (`Phoenix.LiveView.JS`), which
execute directly on the client without reaching the server. To learn more,
see [our bindings page](bindings.md) for a complete list of all LiveView
bindings as well as our [JavaScript interoperability guide](js-interop.md).
## Compartmentalize state, markup, and events in LiveView
LiveView supports two extension mechanisms: function components, provided by
`HEEx` templates, and stateful components.
Function components are any function that receives an assigns map, similar
to `render(assigns)` in our LiveView, and returns a `~H` template. For example:
def weather_greeting(assigns) do
~H"""
<div title="My div" class={@class}>
<p>Hello <%= @name %></p>
<MyApp.Weather.city name="Kraków"/>
</div>
"""
end
You can learn more about function components in the `Phoenix.Component`
module. At the end of the day, they are useful mechanism to reuse markup
in your LiveViews.
However, sometimes you need to compartmentalize or reuse more than markup.
Perhaps you want to move part of the state or part of the events in your
LiveView to a separate module. For these cases, LiveView provides
`Phoenix.LiveComponent`, which are rendered using
[`live_component/1`](`Phoenix.Component.live_component/1`):
<.live_component module={UserComponent} id={user.id} user={user} />
Components have their own `c:mount/3` and `c:handle_event/3` callbacks, as
well as their own state with change tracking support. Components are also
lightweight as they "run" in the same process as the parent `LiveView`.
However, this means an error in a component would cause the whole view to
fail to render. See `Phoenix.LiveComponent` for a complete rundown on components.
Finally, if you want complete isolation between parts of a LiveView, you can
always render a LiveView inside another LiveView by calling
[`live_render/3`](`Phoenix.Component.live_render/3`). This child LiveView
runs in a separate process than the parent, with its own callbacks. If a child
LiveView crashes, it won't affect the parent. If the parent crashes, all children
are terminated.
When rendering a child LiveView, the `:id` option is required to uniquely
identify the child. A child LiveView will only ever be rendered and mounted
a single time, provided its ID remains unchanged.
Given that a LiveView runs on its own process, it is an excellent tool for creating
completely isolated UI elements, but it is a slightly expensive abstraction if
all you want is to compartmentalize markup or events (or both).
To sum it up:
* use `Phoenix.Component` to compartmentalize/reuse markup
* use `Phoenix.LiveComponent` to compartmentalize state, markup, and events
* use nested `Phoenix.LiveView` to compartmentalize state, markup, events, and error isolation
## Endpoint configuration
LiveView accepts the following configuration in your endpoint under
the `:live_view` key:
* `:signing_salt` (required) - the salt used to sign data sent
to the client
* `:hibernate_after` (optional) - the idle time in milliseconds allowed in
the LiveView before compressing its own memory and state.
Defaults to 15000ms (15 seconds)
## Guides
LiveView has many guides to help you on your journey.
### Server-side
These guides focus on server-side functionality:
* [Assigns and HEEx templates](assigns-eex.md)
* [Error and exception handling](error-handling.md)
* [Live Layouts](live-layouts.md)
* [Live Navigation](live-navigation.md)
* [Security considerations of the LiveView model](security-model.md)
* [Telemetry](telemetry.md)
* [Uploads](uploads.md)
* [Using Gettext for internationalization](using-gettext.md)
### Client-side
These guides focus on LiveView bindings and client-side integration:
* [Bindings](bindings.md)
* [Form bindings](form-bindings.md)
* [DOM patching and temporary assigns](dom-patching.md)
* [JavaScript interoperability](js-interop.md)
* [Uploads (External)](uploads-external.md)
'''
alias Phoenix.LiveView.Socket
@type unsigned_params :: map
@doc """
The LiveView entry-point.
For each LiveView in the root of a template, `c:mount/3` is invoked twice:
once to do the initial page load and again to establish the live socket.
It expects three arguments:
* `params` - a map of string keys which contain public information that
can be set by the user. The map contains the query params as well as any
router path parameter. If the LiveView was not mounted at the router,
this argument is the atom `:not_mounted_at_router`
* `session` - the connection session
* `socket` - the LiveView socket
It must return either `{:ok, socket}` or `{:ok, socket, options}`, where
`options` is one of:
* `:temporary_assigns` - a keyword list of assigns that are temporary
and must be reset to their value after every render. Note that once
the value is reset, it won't be re-rendered again until it is explicitly
assigned
* `:layout` - the optional layout to be used by the LiveView
"""
@callback mount(
params :: unsigned_params() | :not_mounted_at_router,
session :: map,
socket :: Socket.t()
) ::
{:ok, Socket.t()} | {:ok, Socket.t(), keyword()}
@doc """
Renders a template.
This callback is invoked whenever LiveView detects
new content must be rendered and sent to the client.
If you define this function, it must return a template
defined via the `Phoenix.Component.sigil_H/2`.
If you don't define this function, LiveView will attempt
to render a template in the same directory as your LiveView.
For example, if you have a LiveView named `MyApp.MyCustomView`
inside `lib/my_app/live_views/my_custom_view.ex`, Phoenix
will look for a template at `lib/my_app/live_views/my_custom_view.html.heex`.
"""
@callback render(assigns :: Socket.assigns()) :: Phoenix.LiveView.Rendered.t()
@doc """
Invoked when the LiveView is terminating.
In case of errors, this callback is only invoked if the LiveView
is trapping exits. See `c:GenServer.terminate/2` for more info.
"""
@callback terminate(reason, socket :: Socket.t()) :: term
when reason: :normal | :shutdown | {:shutdown, :left | :closed | term}
@doc """
Invoked after mount and whenever there is a live patch event.
It receives the current `params`, including parameters from
the router, the current `uri` from the client and the `socket`.
It is invoked after mount or whenever there is a live navigation
event caused by `push_patch/2` or `<.link patch={...}>`.
It must always return `{:noreply, socket}`, where `:noreply`
means no additional information is sent to the client.
"""
@callback handle_params(unsigned_params(), uri :: String.t(), socket :: Socket.t()) ::
{:noreply, Socket.t()}
@doc """
Invoked to handle events sent by the client.
It receives the `event` name, the event payload as a map,
and the socket.
It must return `{:noreply, socket}`, where `:noreply` means
no additional information is sent to the client, or
`{:reply, map(), socket}`, where the given `map()` is encoded
and sent as a reply to the client.
"""
@callback handle_event(event :: binary, unsigned_params(), socket :: Socket.t()) ::
{:noreply, Socket.t()} | {:reply, map, Socket.t()}
@doc """
Invoked to handle calls from other Elixir processes.
See `GenServer.call/3` and `c:GenServer.handle_call/3`
for more information.
"""
@callback handle_call(msg :: term, {pid, reference}, socket :: Socket.t()) ::
{:noreply, Socket.t()} | {:reply, term, Socket.t()}
@doc """
Invoked to handle casts from other Elixir processes.
See `GenServer.cast/2` and `c:GenServer.handle_cast/2`
for more information. It must always return `{:noreply, socket}`,
where `:noreply` means no additional information is sent
to the process which cast the message.
"""
@callback handle_cast(msg :: term, socket :: Socket.t()) ::
{:noreply, Socket.t()}
@doc """
Invoked to handle messages from other Elixir processes.
See `Kernel.send/2` and `c:GenServer.handle_info/2`
for more information. It must always return `{:noreply, socket}`,
where `:noreply` means no additional information is sent
to the process which sent the message.
"""
@callback handle_info(msg :: term, socket :: Socket.t()) ::
{:noreply, Socket.t()}
@optional_callbacks mount: 3,
terminate: 2,
handle_params: 3,
handle_event: 3,
handle_call: 3,
handle_info: 2,
handle_cast: 2
@doc """
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
* `:namespace` - configures the namespace the `LiveView` is in
* `:container` - configures the container the `LiveView` will be wrapped in
* `:layout` - configures the layout the `LiveView` will be rendered in
* `:log` - configures the log level for the `LiveView`
* `:global_prefixes` - the global prefixes to use for components. See
`Global Attributes` in `Phoenix.Component` for more information.
"""
defmacro __using__(opts) do
# Expand layout if possible to avoid compile-time dependencies
opts =
with true <- Keyword.keyword?(opts),
{layout, template} <- Keyword.get(opts, :layout) do
layout = Macro.expand(layout, %{__CALLER__ | function: {:__live__, 0}})
Keyword.replace!(opts, :layout, {layout, template})
else
_ -> opts
end
quote bind_quoted: [opts: opts] do
import Phoenix.LiveView
@behaviour Phoenix.LiveView
@before_compile Phoenix.LiveView.Renderer
@phoenix_live_opts opts
Module.register_attribute(__MODULE__, :phoenix_live_mount, accumulate: true)
@before_compile Phoenix.LiveView
# Phoenix.Component must come last so its @before_compile runs last
use Phoenix.Component, Keyword.take(opts, [:global_prefixes])
end
end
defmacro __before_compile__(env) do
opts = Module.get_attribute(env.module, :phoenix_live_opts)
layout =
case opts[:layout] do
{mod, template} when is_atom(mod) and is_binary(template) ->
root_template = Phoenix.LiveView.Utils.normalize_layout(template, "use options")
{mod, root_template}
{mod, template} when is_atom(mod) and is_atom(template) ->
template = Phoenix.LiveView.Utils.normalize_layout(template, "use options")
{mod, to_string(template)}
nil ->
nil
other ->
raise ArgumentError,
":layout expects a tuple of the form {MyLayoutView, \"my_template.html\"}, " <>
"or {MyLayoutView, :my_template}, got: #{inspect(other)}"
end
log =
case Keyword.fetch(opts, :log) do
{:ok, false} -> false
{:ok, log} when is_atom(log) -> log
:error -> :debug
_ -> raise ArgumentError, ":log expects an atom or false, got: #{inspect(opts[:log])}"
end
phoenix_live_mount = Module.get_attribute(env.module, :phoenix_live_mount)
lifecycle = Phoenix.LiveView.Lifecycle.mount(env.module, phoenix_live_mount)
namespace =
opts[:namespace] || env.module |> Module.split() |> Enum.take(1) |> Module.concat()
name = env.module |> Atom.to_string() |> String.replace_prefix("#{namespace}.", "")
container = opts[:container] || {:div, []}
live = %{
container: container,
name: name,
kind: :view,
module: env.module,
layout: layout,
lifecycle: lifecycle,
log: log
}
quote do
@doc false
def __live__ do
unquote(Macro.escape(live))
end
end
end
@doc """
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
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
"""
defmacro on_mount(mod_or_mod_arg) do
mod_or_mod_arg =
if Macro.quoted_literal?(mod_or_mod_arg) do
Macro.prewalk(mod_or_mod_arg, &expand_alias(&1, __CALLER__))
else
mod_or_mod_arg
end
quote do
Module.put_attribute(
__MODULE__,
:phoenix_live_mount,
Phoenix.LiveView.Lifecycle.on_mount(__MODULE__, unquote(mod_or_mod_arg))
)
end
end
defp expand_alias({:__aliases__, _, _} = alias, env),
do: Macro.expand(alias, %{env | function: {:on_mount, 4}})
defp expand_alias(other, _env), do: other
@doc """
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
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
"""
def connected?(%Socket{transport_pid: transport_pid}), do: transport_pid != nil
@doc """
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
iex> put_flash(socket, :info, "It worked!")
iex> put_flash(socket, :error, "You can't access that page")
"""
defdelegate put_flash(socket, kind, msg), to: Phoenix.LiveView.Utils
@doc """
Clears the flash.
## Examples
iex> clear_flash(socket)
"""
defdelegate clear_flash(socket), to: Phoenix.LiveView.Utils
@doc """
Clears a key from the flash.
## Examples
iex> clear_flash(socket, :info)
"""
defdelegate clear_flash(socket, key), to: Phoenix.LiveView.Utils
@doc """
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
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
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()
)
"""
defdelegate push_event(socket, event, payload), to: Phoenix.LiveView.Utils
@doc ~S"""
Allows an upload for the provided name.
## 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
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
"""
defdelegate allow_upload(socket, name, options), to: Phoenix.LiveView.Upload
@doc """
Revokes a previously allowed upload from `allow_upload/3`.
## Examples
disallow_upload(socket, :avatar)
"""
defdelegate disallow_upload(socket, name), to: Phoenix.LiveView.Upload
@doc """
Cancels an upload for the given entry.
## 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
"""
defdelegate cancel_upload(socket, name, entry_ref), to: Phoenix.LiveView.Upload
@doc """
Returns the completed and in progress entries for the upload.
## Examples
case uploaded_entries(socket, :photos) do
{[_ | _] = completed, []} ->
# all entries are completed
{[], [_ | _] = in_progress} ->
# all entries are still in progress
end
"""
defdelegate uploaded_entries(socket, name), to: Phoenix.LiveView.Upload
@doc ~S"""
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
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
"""
defdelegate consume_uploaded_entries(socket, name, func), to: Phoenix.LiveView.Upload
@doc ~S"""
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
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
"""
defdelegate consume_uploaded_entry(socket, entry, func), to: Phoenix.LiveView.Upload
@doc """
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
* `: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
"""
def redirect(socket, opts \\ [])
def redirect(%Socket{} = socket, to: url) do
validate_local_url!(url, "redirect/2")
put_redirect(socket, {:redirect, %{to: url}})
end
def redirect(%Socket{} = socket, external: url) do
case url do
{scheme, rest} ->
put_redirect(socket, {:redirect, %{external: "#{scheme}:#{rest}"}})
url when is_binary(url) ->
external_url = Phoenix.LiveView.Utils.valid_string_destination!(url, "redirect/2")
put_redirect(socket, {:redirect, %{external: external_url}})
other ->
raise ArgumentError,
"expected :external option in redirect/2 to be valid URL, got: #{inspect(other)}"
end
end
def redirect(%Socket{}, _) do
raise ArgumentError, "expected :to or :external option in redirect/2"
end
@doc """
Annotates the socket for navigation within the current LiveView.
When navigating to the current LiveView, `c: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
* `: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
{:noreply, push_patch(socket, to: "/")}
{:noreply, push_patch(socket, to: "/", replace: true)}
"""
def push_patch(%Socket{} = socket, opts) do
opts = push_opts!(opts, "push_patch/2")
put_redirect(socket, {:live, :patch, opts})
end
@doc """
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
* `: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
{:noreply, push_navigate(socket, to: "/")}
{:noreply, push_navigate(socket, to: "/", replace: true)}
"""
def push_navigate(%Socket{} = socket, opts) do
opts = push_opts!(opts, "push_navigate/2")
put_redirect(socket, {:live, :redirect, opts})
end
@doc """
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
* `: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
{:noreply, push_redirect(socket, to: "/")}
{:noreply, push_redirect(socket, to: "/", replace: true)}
"""
@doc deprecated: "Use push_navigate/2 instead"
# Deprecate in 0.19
def push_redirect(%Socket{} = socket, opts) do
opts = push_opts!(opts, "push_redirect/2")
put_redirect(socket, {:live, :redirect, opts})
end
defp push_opts!(opts, context) do
to = Keyword.fetch!(opts, :to)
validate_local_url!(to, context)
kind = if opts[:replace], do: :replace, else: :push
%{to: to, kind: kind}
end
defp put_redirect(%Socket{redirected: nil} = socket, command) do
%Socket{socket | redirected: command}
end
defp put_redirect(%Socket{redirected: to} = _socket, _command) do
raise ArgumentError, "socket already prepared to redirect with #{inspect(to)}"
end
@invalid_local_url_chars ["\\"]
defp validate_local_url!("//" <> _ = to, where) do
raise_invalid_local_url!(to, where)
end
defp validate_local_url!("/" <> _ = to, where) do
if String.contains?(to, @invalid_local_url_chars) do
raise ArgumentError, "unsafe characters detected for #{where} in URL #{inspect(to)}"
else
to
end
end
defp validate_local_url!(to, where) do
raise_invalid_local_url!(to, where)
end
defp raise_invalid_local_url!(to, where) do
raise ArgumentError, "the :to option in #{where} expects a path but was #{inspect(to)}"
end
@doc """
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
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
def mount(_params, _session, socket) do
{:ok, assign(socket, width: get_connect_params(socket)["width"] || @width)}
end
"""
def get_connect_params(%Socket{private: private} = socket) do
if connect_params = private[:connect_params] do
if connected?(socket), do: connect_params, else: nil
else
raise_root_and_mount_only!(socket, "connect_params")
end
end
@deprecated "use get_connect_info/2 instead"
def get_connect_info(%Socket{private: private} = socket) do
if connect_info = private[:connect_info] do
if connected?(socket), do: connect_info, else: nil
else
raise_root_and_mount_only!(socket, "connect_info")
end
end
@doc """
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
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.
"""
def get_connect_info(%Socket{private: private} = socket, key) when is_atom(key) do
if connect_info = private[:connect_info] do
case connect_info do
%Plug.Conn{} -> conn_connect_info(connect_info, key)
%{} -> connect_info[key]
end
else
raise_root_and_mount_only!(socket, "connect_info")
end
end
defp conn_connect_info(conn, :peer_data) do
Plug.Conn.get_peer_data(conn)
end
defp conn_connect_info(conn, :x_headers) do
for {header, _} = pair <- conn.req_headers,
String.starts_with?(header, "x-"),
do: pair
end
defp conn_connect_info(conn, :trace_context_headers) do
for {header, _} = pair <- conn.req_headers,
header in ["traceparent", "tracestate"],
do: pair
end
defp conn_connect_info(conn, :uri) do
%URI{
scheme: to_string(conn.scheme),
query: conn.query_string,
port: conn.port,
host: conn.host,
path: conn.request_path
}
end
defp conn_connect_info(conn, :user_agent) do
with {_, value} <- List.keyfind(conn.req_headers, "user-agent", 0) do
value
end
end
@doc """
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.
"""
def static_changed?(%Socket{private: private, endpoint: endpoint} = socket) do
if connect_params = private[:connect_params] do
connected?(socket) and
static_changed?(
connect_params["_track_static"],
endpoint.config(:cache_static_manifest_latest)
)
else
raise_root_and_mount_only!(socket, "static_changed?")
end
end
defp static_changed?([_ | _] = statics, %{} = latest) do
latest = Map.to_list(latest)
not Enum.all?(statics, fn static ->
[static | _] = :binary.split(static, "?")
Enum.any?(latest, fn {non_digested, digested} ->
String.ends_with?(static, non_digested) or String.ends_with?(static, digested)
end)
end)
end
defp static_changed?(_, _), do: false
defp raise_root_and_mount_only!(socket, fun) do
if child?(socket) do
raise RuntimeError, """
attempted to read #{fun} from a nested child LiveView #{inspect(socket.view)}.
Only the root LiveView has access to #{fun}.
"""
else
raise RuntimeError, """
attempted to read #{fun} outside of #{inspect(socket.view)}.mount/3.
#{fun} only exists while mounting. If you require access to this information
after mount, store the state in socket assigns.
"""
end
end
@doc """
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`](`c:Phoenix.LiveComponent.preload/1`) then
[`update/2`](`c:Phoenix.LiveComponent.update/2`) is invoked with the new assigns.
If [`update/2`](`c:Phoenix.LiveComponent.update/2`) is not defined
all assigns are simply merged into the socket.
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`](`c:Phoenix.LiveComponent.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
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
"""
def send_update(pid \\ self(), module, assigns) when is_atom(module) and is_pid(pid) do
assigns = Enum.into(assigns, %{})
id =
assigns[:id] ||
raise ArgumentError, "missing required :id in send_update. Got: #{inspect(assigns)}"
Phoenix.LiveView.Channel.send_update(pid, module, id, assigns)
end
@doc """
Similar to `send_update/3` but the update will be delayed according to the given `time_in_milliseconds`.
## 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
"""
def send_update_after(pid \\ self(), module, assigns, time_in_milliseconds)
when is_atom(module) and is_integer(time_in_milliseconds) and is_pid(pid) do
assigns = Enum.into(assigns, %{})
id =
assigns[:id] ||
raise ArgumentError, "missing required :id in send_update_after. Got: #{inspect(assigns)}"
Phoenix.LiveView.Channel.send_update_after(pid, module, id, assigns, time_in_milliseconds)
end
@doc """
Returns the transport pid of the socket.
Raises `ArgumentError` if the socket is not connected.
## Examples
iex> transport_pid(socket)
#PID<0.107.0>
"""
def transport_pid(%Socket{}) do
case Process.get(:"$callers") do
[transport_pid | _] -> transport_pid
_ -> raise ArgumentError, "transport_pid/1 may only be called when the socket is connected."
end
end
defp child?(%Socket{parent_pid: pid}), do: is_pid(pid)
@doc """
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](js-interop.html#client-hooks).
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. Hooks may be attached to any of the following
lifecycle stages: `:mount` (via `on_mount/1`), `:handle_params`,
`:handle_event`, and `:handle_info`.
## Return Values
Lifecycle hooks take place immediately before a given lifecycle
callback is invoked on the LiveView. 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.
## 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
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
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.
## Examples
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
"""
defdelegate attach_hook(socket, name, stage, fun), to: Phoenix.LiveView.Lifecycle
@doc """
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](js-interop.html#client-hooks).
If no hook is found, this function is a no-op.
## Examples
def handle_event(_, socket) do
{:noreply, detach_hook(socket, :hook_that_was_attached, :handle_event)}
end
"""
defdelegate detach_hook(socket, name, stage), to: Phoenix.LiveView.Lifecycle
end
