Undefined method "has_attached_file" for my ActiveRecord model

Question

I followed the docs at https://github.com/thoughtbot/paperclip exactly to install implement paperclip in my app for image uploading. I am currently using gem 'paperclip', '~> 5.0.0.beta1'. After I did the migration, the four columns were added onto my schema properly:

t.string   "picture_file_name"
t.string   "picture_content_type"
t.integer  "picture_file_size"
t.datetime "picture_updated_at"

My paperclip should therefore be installed correctly. However, when I proceeded to add the following two lines onto my model class:

  has_attached_file :picture, styles: { medium: "300*300>", thumb: "100*100" }, default_url: "/images/start_project3.jpg"
  validates_attachment_content_type :picture, content_type: /\Aimage\/.*\Z/

Everything broke. I try to create, search, or anything related to the model class in rails console, it yells at me with the following error:

NoMethodError: undefined method `has_attached_file' for #<Class:0x0055bd71ec0228>

I have tried multiple versions of paperclip, from the earlier version 4.3.0 to the latest version of paperclip, but the problem persists. I also restarted my server in between changes and migrations, but that did not fix the problem. This is the migration that I performed:

class AddAttachmentPictureToProjects < ActiveRecord::Migration
  def self.up
    change_table :projects do |t|
      t.attachment :picture
    end
  end

  def self.down
    remove_attachment :projects, :picture
  end
end

I am totally lost right now as to what to do. This is my gem file:

source 'https://rubygems.org'


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.2.7.1'
# Use postgresql as the database for Active Record
gem 'pg', '~> 0.15'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.1.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.0'
# bundle exec rake doc:rails generates the API under doc/api.
gem 'sdoc', '~> 0.4.0', group: :doc

# Use ActiveModel has_secure_password
gem 'bcrypt', '~> 3.1.7'
gem 'pry-rails'
gem 'annotate'
# Use Unicorn as the app server
# gem 'unicorn'
gem 'faker'
# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development
gem 'pg_search'
gem 'paperclip', '~> 5.0.0.beta1'
# gem "paperclip", :git => "git://github.com/thoughtbot/paperclip.git"
# gem "paperclip", "~> 4.3"

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug'
  gem 'faker'
end

group :development do
  # Access an IRB console on exception pages or by using <%= console %> in views
  gem 'web-console', '~> 2.0'

  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
end

group :production do
  gem 'newrelic_rpm'
  gem 'rails_12factor' # error feedback
end

Answer 1

I am not sure what happened. I ended up doing a db roll back and re-migrated the migration yet again. Then I exited all my terminals running in the background and restarted everything. It is working as of now.