NameError uninitialized class variable @@gallery in > PropertiesController Did you mean? caller

Question

after setup a image gallery for post the logs spit out this

NameError (uninitialized class variable @@gallery in PropertiesController Did you mean? caller):

Issue

So i tried to remove a @ from the variable! the thing is just a image galler for the post, and i received the code with 2 @@ as im new to ruby this context using 2 @@ for variable, why?

but still with the issue, please someone can spare a hint?

Post controller

class PropertiesController < ApplicationController
  before_action :authenticate_admin!, except: [:home, :index, :show]
  include ApplicationHelper

  def show
    @property = Property.find(params[:id])
    @question = params[:question]
  end

  def new() initialize_form end

  def edit() initialize_form end

  def get_images() render json: {images: @@gallery.images} end




  def create
    @property = property_type.new property_params
    @property.gallery = @@gallery


    unmask_fields

    if @property.save
      @@gallery.save if @@gallery
      redirect_to @property, flash: { notice: "Criado com sucessso!" }
    else
      render "properties/new_or_edit"
    end
  end



  def add_image
    images = @@gallery.images
    images << image_param[:image]
    @@gallery.images = images

    if @@gallery.valid?
      # if @@gallery.save
      render json: {images: @@gallery.images}
      # end
    else
      render json: @@gallery.errors.messages, status: 406
      @@gallery.images.pop
    end
  end


  def remove_image
    remain_images = @@gallery.images
    deleted_image = remain_images.delete_at(params[:index].to_i) # delete the target image
    @@gallery.images = remain_images

    if @@gallery.valid?
      if @@gallery.save
        render json: {images: @@gallery.images}
        deleted_image.try(:remove!) # delete image from S3
      end
    else
      render json: @@gallery.errors.messages, status: 400
    end
  end

  def set_main_image
    images = @@gallery.images
    images.insert(0, images.delete_at(params[:index].to_i))
    @@gallery.images = images

    if @@gallery.valid?
      render json: {images: @@gallery.images}
    else
      render json: @@gallery.errors.messages, status: 400
    end
  end

  def initialize_form
    @property = property_type.find(params[:id]) if params[:id]
    @property ||= property_type.new

    @@gallery = @property.gallery || Gallery.new


    render "properties/new_or_edit"
  end

  private

  def property_params
    params.require(params[:type].downcase.to_sym).permit PROPERTY_PARAMS

  end




  def image_param
    params.permit(:image)
  end



  def property_id
    if params[:type] then params["#{params[:type].downcase}_id".to_sym] else nil end
  end

  def property_name
    "#{params[:type].downcase}"
  end

  def property_type
    params[:type].constantize if params[:type].in? PROPERTY_TYPES
  end

end