Class: LiveRecord::PublicationsChannel

Inherits:
BaseChannel
  • Object
show all
Defined in:
app/channels/live_record/publications_channel.rb

Overview

This channel streams new records to connected clients whenever the “where” condition supplied by the client matches This implementation can be quite inefficient because there’s only one pub-sub queue used for each model, but because of constraints ( see github.com/jrpolidario/live_record/issues/2 ) and because Users are authorised-validated anyway in each stream, then there’s already an overhead delay. I am prioritising development convenience (as Rails does), in order to achieve a simpler API; in this example, it would be something like in JS: ‘LiveRecord.Model.all.Book.subscribe(is_enabled: true)`

Instance Method Summary collapse

Instance Method Details

#subscribed ⇒ Object 



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# File 'app/channels/live_record/publications_channel.rb', line 9

def subscribed
  model_class = params[:model_name].safe_constantize

  if !(model_class && model_class < ApplicationRecord)
    respond_with_error(:bad_request, 'Not a correct model name')
    reject_subscription
  end

  if !(model_class && LiveRecord::BaseChannel::Helpers.queryable_attributes(model_class, current_user).present?)
    respond_with_error(:forbidden, 'You do not have privileges to query')
    reject_subscription
  end

  stream_from "live_record:publications:#{params[:model_name].underscore}", coder: ActiveSupport::JSON do |message|
    newly_created_record = model_class.find(message['attributes']['id'])

    active_record_relation = LiveRecord::BaseChannel::SearchAdapters.mapped_active_record_relation(
      model_class: model_class,
      conditions_hash: params[:where].to_h,
      current_user: current_user
    )

    if active_record_relation.exists?(id: newly_created_record.id)
      whitelisted_attributes = LiveRecord::BaseChannel::Helpers.whitelisted_attributes(newly_created_record, current_user)

      if whitelisted_attributes.size > 0
        message = { 'action' => 'create', 'attributes' => message['attributes'] }
        response = filtered_message(message, whitelisted_attributes)
        transmit response if response.present?
      end
    end
  end
end

#sync_records(data) ⇒ Object

TODO: split up sync_records action because it currently both handles “syncing” and “reloading”



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# File 'app/channels/live_record/publications_channel.rb', line 44

def sync_records(data)
  params = data.symbolize_keys
  model_class = params[:model_name].safe_constantize

  if model_class && model_class < ApplicationRecord
    is_being_reloaded = params[:stale_since].blank?
    is_being_synced = params[:stale_since].present?

    active_record_relation = LiveRecord::BaseChannel::SearchAdapters.mapped_active_record_relation(
      model_class: model_class,
      conditions_hash: params[:where].to_h,
      current_user: current_user,
    )

    if is_being_synced
      active_record_relation = active_record_relation.where(
        'created_at >= ?', DateTime.parse(params[:stale_since]) - LiveRecord.configuration.sync_record_buffer_time
      )
    end

    # we `transmmit` a message back to client for each matching record
    active_record_relation.find_each do |record|
      # but first, check for the authorised attributes, if exists
      whitelisted_attributes = LiveRecord::BaseChannel::Helpers.whitelisted_attributes(record, current_user)

      if whitelisted_attributes.size > 0
        message = { 'action' => 'create', 'attributes' => record.attributes }
        response = filtered_message(message, whitelisted_attributes)
        transmit response if response.present?
      end
    end

    # if being reloaded, we finally still transmit a "done" action indicating that reloading has just finished
    if is_being_reloaded
      response = { 'action' => 'afterReload', 'recordIds' => active_record_relation.pluck(:id) }
      transmit response
    end
  else
    respond_with_error(:bad_request, 'Not a correct model name')
    reject_subscription
  end
end