Rails vs. Websockets：在模型更改时触发控制器方法

Question

I'm currently working on a rails app. The app takes temperature data via a daemon (running in the background). Every time a new temperature object is saved and the temperature exceeds a certain level, I want to display the new data to the user (asynchronous via websockets).

To handle the websocket communication, the websocket-rails gem is used ( https://github.com/websocket-rails/websocket-rails ).

The websocket communication itself works fine. But I don't know how to trigger the websocket controller method on a model change, without breaking the mvc principles.

Is there a clean way to solve this problem?

Additional information:

Currently the daemon adds a temperature object every 20 seconds. But this value depends on settings and the count of measurement points.

temperature model:

# == Schema Information
#
# Table name: measurements
#
#  id          :integer          not null, primary key
#  value       :float
#  measured_at :datetime
#  created_at  :datetime
#  updated_at  :datetime
#

class Measurement < ActiveRecord::Base

end

The daemon uses different external sources (I don't think details matter that much) and creates new objects:

newTemp = Measurement.new
# set values ...
newTemp.save

Answer 1

I think you need to use this, as docs says:

Broadcast to the channel from anywhere inside your Rails application. An existing controller, a model, a background job, or a new WebsocketRails controller.

latest_post = Post.latest
WebsocketRails[:posts].trigger 'new', latest_post

check it out: Documentation

Answer 2

Daemon should post new temperature objects through a controller interface, just like a regular web request. Accessing objects directly (not via controller) breaks the MVC pattern.

My suggestion is to implement trigger_value:float and triggered?:boolean attributes in Temperature .

• (Controller, before save) Pass a trigger value along with temperature daemon data to a new Temperature object.

• (Model, during save) Calculate whether temperature value exceeds trigger value; set triggered? boolean accordingly.

• (Controller, after save) After create, read the triggered? boolean; publish message to client if necessary.