我想获取使用phoenix框架编写的小型聊天应用程序的用户状态。
状态：在线/离线/忙碌/离开
这是注释的代码段：
defmodule PhoenixChat.Presence do
@moduledoc """
Provides presence tracking to channels and processes.
See the [`Phoenix.Presence`](http://hexdocs.pm/phoenix/Phoenix.Presence.html)
docs for more details.
## Usage
Presences can be tracked in your channel after joining:
defmodule PhoenixChat.MyChannel do
use PhoenixChat.Web, :channel
alias PhoenixChat.Presence
def join("some:topic", _params, socket) do
send(self, :after_join)
{:ok, assign(socket, :user_id, ...)}
end
def handle_info(:after_join, socket) do
{:ok, _} = Presence.track(socket, socket.assigns.user_id, %{
online_at: inspect(System.system_time(:seconds))
})
push socket, "presence_state", Presence.list(socket)
{:noreply, socket}
end
end
In the example above, `Presence.track` is used to register this
channel's process as a presence for the socket's user ID, with
a map of metadata. Next, the current presence list for
the socket's topic is pushed to the client as a `"presence_state"` event.
Finally, a diff of presence join and leave events will be sent to the
client as they happen in real-time with the "presence_diff" event.
See `Phoenix.Presence.list/2` for details on the presence datastructure.
## Fetching Presence Information
The `fetch/2` callback is triggered when using `list/1`
and serves as a mechanism to fetch presence information a single time,
before broadcasting the information to all channel subscribers.
This prevents N query problems and gives you a single place to group
isolated data fetching to extend presence metadata.
The function receives a topic and map of presences and must return a
map of data matching the Presence datastructure:
%{"123" => %{metas: [%{status: "away", phx_ref: ...}],
"456" => %{metas: [%{status: "online", phx_ref: ...}]}
The `:metas` key must be kept, but you can extend the map of information
to include any additional information. For example:
def fetch(_topic, entries) do
query =
from u in User,
where: u.id in ^Map.keys(entries),
select: {u.id, u}
users = query |> Repo.all |> Enum.into(%{})
for {key, %{metas: metas}} <- entries, into: %{} do
{key, %{metas: metas, user: users[key]}}
end
end
The function above fetches all users from the database who
have registered presences for the given topic. The fetched
information is then extended with a `:user` key of the user's
information, while maintaining the required `:metas` field from the
original presence data.
"""
use Phoenix.Presence, otp_app: :phoenix_chat,
pubsub_server: PhoenixChat.PubSub
end
我正在使用此方法获取用户状态PhoenixChat.RoomChannel
def handle_info(:after_join, socket) do
Presence.track(socket, socket.assigns.user, %{
online_at: :os.system_time(:millisecond)
})
push socket, "presence_state", Presence.list(socket)
{:noreply, socket}
end
在此部分中 保存用户状态
def connect(%{"user" => user, "status" => status}, socket) do
Redix.command(:redix, ["SET", user, status])
{:ok, assign(socket, :user, user)}
end
我想获得状态而不是时间。 如何执行此任务？
您正在传递一个地图，其中online_at作为Presence.track/3的第三个参数。您可以将任何其他字段放入其中以跟踪状态。请注意，当您要更改状态时，必须再次拨打Presence.track/3。