I'm stuck while creating a file-uploading web page with dropzone

Question

I was following a tutorial about developing a DropBox like file sharing platform using dropzone, ruby on rails and Ajax. I created a rails application, integrated dropzone into the project, created paperclip and uploads models. Everything was okay till I edited UPLOADS_CONTROLLER.RB file as follows:

class UploadsController < ApplicationController
  def new
    @upload = Upload.new
  end

  def create
    @upload = Upload.create(upload_params)
    if @upload.save
      render json: { message: "success" }, :status => 200
    else
      #  you need to send an error header, otherwise Dropzone
          #  will not interpret the response as an error:
      render json: { error: @upload.errors.full_messages.join(',')}, :status => 400
    end         
  end

  private
  def upload_params
    params.require(:upload).permit(:image)
  end
end

After editing the file, I reloaded the page and I got the error below. I can't fix the problem. Thanks for your help!

TypeError in UploadsController#new
superclass mismatch for class Upload
Extracted source (around line #3):
1 class Upload ApplicationRecord
2 end
3 class Upload < ActiveRecord::Base
4 has_attached_file :image, :styles => { :medium => "300x300>",:thumb => "100x100>" }
5
6 validates_attachment :image,
Application Trace | Framework Trace | Full Trace app/models/upload.rb:3:in <top (required)>'
app/controllers/uploads_controller.rb:3:innew'

Link to the tutorial which I mentioned

Answer 1

You probably have a UploadsController class defined elsewhere, it could be the second time you declared it or one of your Gems or plugins already defines it.