存在

使用实时在线状态来跟踪多个用户之间的状态。

🌐 Use Realtime Presence to track state between multiple users.

用法 #

🌐 Usage

你可以使用 Supabase 客户端库来跟踪用户之间的在线状态。

🌐 You can use the Supabase client libraries to track Presence state between users.

Presence 是如何运作的 #

🌐 How Presence works

Presence 让每个连接的客户端发布一小部分状态——称为“presence 负载”——到共享通道。Supabase 会将每个客户端的负载存储在一个唯一的 presence 键下，并保持所有连接客户端的合并视图。

🌐 Presence lets each connected client publish a small piece of state—called a “presence payload”—to a shared channel. Supabase stores each client’s payload under a unique presence key and keeps a merged view of all connected clients.

当任何客户端订阅、断开连接或更新他们的状态信息时，Supabase 会触发以下三种事件之一：

🌐 When any client subscribes, disconnects, or updates their presence payload, Supabase triggers one of three events:

• sync — 完整状态已更新
• join — 一个新客户开始跟踪出勤了
• leave — 客户端已停止追踪在线状态

presenceState() 返回的完整在线状态看起来是这样的：

🌐 The complete presence state returned by presenceState() looks like this:

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{
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  "client_key_1": [{ "userId": 1, "typing": false }],
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  "client_key_2": [{ "userId": 2, "typing": true }]
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}

初始化客户端 #

🌐 Initialize the client

从项目的 Connect 对话框 获取项目的 URL 和密钥。

🌐 Get the Project URL and key from the project's Connect dialog.

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import { createClient } from '@supabase/supabase-js'
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const SUPABASE_URL = 'https://<project>.supabase.co'
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const SUPABASE_KEY = '<sb_publishable_... key>'
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const supabase = createClient(SUPABASE_URL, SUPABASE_KEY)

同步并跟踪状态 #

🌐 Sync and track state

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const roomOne = supabase.channel('room_01')
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roomOne
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  .on('presence', { event: 'sync' }, () => {
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    const newState = roomOne.presenceState()
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    console.log('sync', newState)
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  })
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  .on('presence', { event: 'join' }, ({ key, newPresences }) => {
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    console.log('join', key, newPresences)
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  })
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  .on('presence', { event: 'leave' }, ({ key, leftPresences }) => {
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    console.log('leave', key, leftPresences)
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  })
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  .subscribe()

发送状态 #

🌐 Sending state

你可以使用 track() 向所有订阅者发送状态：

🌐 You can send state to all subscribers using track():

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const roomOne = supabase.channel('room_01')
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const userStatus = {
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  user: 'user-1',
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  online_at: new Date().toISOString(),
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}
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roomOne.subscribe(async (status) => {
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  if (status !== 'SUBSCRIBED') { return }
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  const presenceTrackStatus = await roomOne.track(userStatus)
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  console.log(presenceTrackStatus)
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})

一个客户端会接收任何订阅了相同主题（在这个例子中是 room_01）的其他客户端的状态。它也会自动触发自身的 sync 和 join 事件处理器。

🌐 A client will receive state from any other client that is subscribed to the same topic (in this case room_01). It will also automatically trigger its own sync and join event handlers.

停止追踪 #

🌐 Stop tracking

你可以使用 untrack() 方法停止追踪出席情况。这将触发 sync 和 leave 事件处理程序。

🌐 You can stop tracking presence using the untrack() method. This will trigger the sync and leave event handlers.

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const untrackPresence = async () => {
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  const presenceUntrackStatus = await roomOne.untrack()
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  console.log(presenceUntrackStatus)
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}
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untrackPresence()

显示选项 #

🌐 Presence options

你可以在初始化 Supabase 客户端时传入配置选项。

🌐 You can pass configuration options while initializing the Supabase Client.

存在键 #

🌐 Presence key

默认情况下，Presence 会在服务器上生成一个唯一的 UUIDv1 密钥来跟踪客户端通道的状态。如果你愿意，可以在创建通道时提供自定义密钥。这个密钥在客户端之间应该是唯一的。

🌐 By default, Presence will generate a unique UUIDv1 key on the server to track a client channel's state. If you prefer, you can provide a custom key when creating the channel. This key should be unique among clients.

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import { createClient } from '@supabase/supabase-js'
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const supabase = createClient('SUPABASE_URL', 'SUPABASE_PUBLISHABLE_KEY')
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const channelC = supabase.channel('test', {
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  config: {
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    presence: {
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      key: 'userId-123',
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    },
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  },
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})