ActionController::Live - SSE in Rails

Question

I want changes in the database to be reflected on the page without server reload.

controller

class ProductController < ApplicationController
  include ActionController::Live

  def index
    @product = Product.available
    response.headers['Content-Type'] = 'text/event-stream'
    sse = SSE.new(response.stream)
    sse.write @product
  ensure
    sse.close
  end
end 

view

<p><%= @product[:price] %></p>

I am using Puma.

When I update the product in the database, the changes are not reflected on the webpage.

What am I missing?

Answer 1

Rails cannot update the view in real time. It serves the html and then it's up to some JavaScript to listen to the stream and handle the events.

I've created a gem, Shower, that handles all of this for you. https://github.com/kpheasey/shower

Using Shower, the solution would be something like this.

First you need to publish the update event, this can be done with an after_update callback on the Product model.

class Product < ActiveRecord::Base
    after_update :publish_event

    def publish_event
        Shower::Stream.publish('product.update', self)
    end
end

Then you need some javascript to listen to the event stream and act on it.

$ ->
    stream = new Shower('/stream', ['product.update'])

    stream.addEventListener('product.update', (event) ->
      product = JSON.parse(event.data)
      $('p').html(product.price)
    )