API sample for mobile app: Here the mobile app is sending a registration token to Rails app so that it can send it messages and push notifications and in events controller the mobile app is creating events on server so that it can be stored and analyzed

devices_controller.rb

class DevicesController < ApplicationController

  before_filter :authenticate_user!

  def create
    @device = current_user.app.devices.new(registration_id: params[:registration_id])
    if params[:platform] && params[:platform].upcase == 'IOS'
      @device.os = :ios
    end
    if @device.save
      respond_to do |format|
        format.json { render json: @device, status: :ok }
      end
    else
      if current_user.app.devices.where(registration_id: params[:registration_id]).exists?
        @device = current_user.app.devices.find_by(registration_id: params[:registration_id])
        @device.update_attribute(:last_registered_at, Time.now)
        respond_to do |format|
          format.json { render json: @device, status: :ok }
        end
      else
        respond_to do |format|
          format.json { render json: @device.errors, status: :unprocessable_entity }
        end
      end
    end
  end

end

events_controller.rb

class EventsController < ApplicationController

  before_filter :authenticate_user!, :load_event_type, :load_device

  def create
    raise ArgumentError if @device.blank? || @event_type.blank?
    @event = @device.events.new(parameters: params[:values])
    @event.event_type = @event_type
    if @event.save
      respond_to do |format|
        format.json {render json: @event, status: :created}
      end
    else
      respond_to do |format|
        format.json {render json: @event.errors, status: :unprocessable_entity}
      end
    end
  rescue ArgumentError
    respond_to do |format|
      format.json {render json: {Error: 'Unknown Device ID or Event Type'}, status: :internal_server_error}
    end
  end
  
  def load_event_type
    if params && params[:event_type]
      @event_type = current_user.app.event_types.where(name: params[:event_type].downcase.to_sym).first
    end
  end

  def load_device
    if params && params[:device_id]
      @device = current_user.app.devices.find(params[:device_id])
    end
  end

end