first commit

app/models/application_record.rb

@@ -0,0 +1,3 @@
+class ApplicationRecord < ActiveRecord::Base
+  primary_abstract_class
+end

app/models/article.rb

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+class Article < ApplicationRecord
+  include Visible
+  
+  has_many :comments, dependent: :destroy
+
+  validates :title, presence: true
+  validates :body, presence: true, length: {minimum: 10}
+end

app/models/comment.rb

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+class Comment < ApplicationRecord
+  include Visible
+
+  belongs_to :article
+end

app/models/concerns/visible.rb

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+module Visible
+  extend ActiveSupport::Concern
+
+  VALID_STATUSES = ['public', 'private', 'archived']
+
+  included do
+    validates :status, inclusion: { in: VALID_STATUSES }
+  end
+
+  class_methods do
+    def public_count
+      where(status: 'public').count
+    end
+  end
+
+  def archived?
+    status == 'archived'
+  end
+end

app/models/user.rb

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+class User < ApplicationRecord
+  has_secure_password
+end