您将如何使用 ActionCable 订阅特定流

Question

我有一个原生 Rails Web 应用和一个带有聊天组件的 iOS 应用。我正在使用 ActionCable 提供实时消息传递。

在MessageController中创建消息时，服务器向MessageChannel中的两个流进行广播

• 渲染的 html 去网络聊天
• 要转到 iOS 应用程序的 json 对象

您可以创建特定于流的订阅吗？也就是在客户端，能不能从json广播中过滤掉html广播？

或者我应该创建一个 ApiMessageChannel 和一个 Web MessageChannel 吗？这感觉像是不必要的重复，因为 create 总是会同时向 web 和 api 广播。

消息频道

class MessageChannel < ApplicationCable::Channel
  def subscribed
    stop_all_streams
    stream_for Group.find(params["id"])
    stream_from "message:messages_api_#{params["id"]}"
  end
end

消息控制器

def create
# ... 

MessageChannel.broadcast_to group, message: render_to_string(message, locals: { previous_message: previous_message, type: group.type, current_user: current_user })

MessageChannel.broadcast_to "messages_api_#{group.id}", message: ApplicationController.render_with_signed_in_user(current_user, json: { sender: current_user.username, content: message.body })
end

聊天室控制器

import { Controller } from "stimulus"
import consumer from "channels/consumer"

export default class extends Controller {
  static targets = [ "messages", "newMessage" ]

  connect() {
    this.subscription = consumer.subscriptions.create({ channel: "MessageChannel", id: this.data.get("id") }, {
      connected: this._connected.bind(this),
      disconnected: this._disconnected.bind(this),
      received: this._received.bind(this)
    })
  }

  disconnect() {
    consumer.subscriptions.remove(this.subscription)
  }

  _connected() {
  }

  _disconnected() {
  }

  _received(data) {
    if (data.message) {
      this.messagesTarget.insertAdjacentHTML('beforeend', data.message);
      $('.js-chat-messages').scrollTop($('.js-chat-messages')[0].scrollHeight);
    }
  }

  clearMessage(event) {
    this.newMessageTarget.value = ''
  }
}

Swift iOS

static var ChannelIdentifier = "MessageChannel"
    let actionCableClient = ActionCableClient(url: URL(string: "wss://localhost:3000/cable")!)

        actionCableClient.headers = [
            "Authorization": token,
            "Accept": "application/json"
        ]
        
        actionCableClient.connect()

        let room_identifier = ["id" : "12"]
        actionCableChannel = actionCableClient.create(ActionCableController.ChannelIdentifier, parameters: room_identifier, autoSubscribe: true, bufferActions: true )

actionCableChannel?.onReceive = { (data: Any?, error: Error?) in
            print("recieved message!")
            if let error = error {
                print("ERROR: Unable to receive message from ActionCable Channel: \(error.localizedDescription)")
                return
            }
    ```

Answer 1

要订阅特定的命名流，您可以：

class MessageChannel < ApplicationCable::Channel
  def subscribed
    # stream_from "message:messages_web"
    # stream_from "message:messages_api"
    # stream_from "message:messages_test"

    stream_from "message:messages_#{params[:type]}"

    # !! can also add in other parameters and add those on the client side for stream specific filtering
    # stream_from "message:messages_#{params[:type]}_#{params[:id]}"

  end
end

class MessagesController < ApplicationController
  def create
    MessageChannel.broadcast_to "messages_web", 'web'
    MessageChannel.broadcast_to "messages_api", 'api'
    MessageChannel.broadcast_to "messages_test", 'test'
  end
end

import consumer from "channels/consumer"
this.subscription = consumer.subscriptions.create({ channel: "MessageChannel", type: 'web'}, {
  connected: this._connected.bind(this),
  disconnected: this._disconnected.bind(this),
  received: this._received.bind(this)
})

这只会接收来自“message:messages_web”的消息

Answer 2

根据文档，你可以知道如下：

发现订阅的方法是通过客户端javascript调用的，而不是由rails控制器调用的。

根据你的问题，你应该订阅特殊资源吧？