class User < ActiveRecord::Base
    # id:integer name:string deleted:boolean

    has_many :posts
end

class Post < ActiveRecord::Base
    # id:integer user_id:integer content:string deleted:boolean

    belongs_to :user
end

class Post < ActiveRecord::Base
    # id:integer user_id:integer content:string deleted:boolean

    belongs_to :user

    def administrated_content
       if !self.deleted
          self.content
       else
          "This post has been removed"
       end
    end
end

class State
    #id:integer #deleted:boolean #deleted_by:integer

    belongs_to :user
    belongs_to :post
end

class Post < ActiveRecord::Base
  scope :not_deleted, lambda { where(deleted_at: nil) }
  scope :deleted, lambda { where("#{self.table_name}.deleted_at IS NOT NULL") }

  def destroy
    self.update_attributes(deleted_at: DateTime.current)
  end

  def delete
    destroy
  end

  def deleted?
    self.deleted_at.present?
  end
  # ...

# lib/extensions/act_as_fake_deletable.rb
module ActAsFakeDeletable
  # override the model actions
  def delete
    self.update_attributes(:deleted_at, DateTime.current)
  end
  def destroy
    self.update_attributes(:deleted_at, DateTime.current)
  end

  # define new scopes
  def self.included(base)
    base.class_eval do
      scope :deleted, where('deleted_at IS NOT NULL')
      scope :not_deleted, where('deleted_at IS NULL')

      scope :destroyed, where('deleted_at IS NOT NULL')
      scope :not_destroyed, where('deleted_at IS NULL')
    end
  end
end

class ActiveRecord::Base
  def self.act_as_fake_deletable(options = {})
    alias_method :destroy!, :destroy
    alias_method :delete!, :delete
    include ActAsFakeDeletable

    options = { field_to_hide: :content, message_to_show_instead: "This content has been deleted" }.merge!(options)

    define_method options[:field_to_hide].to_sym do
      return options[:message_to_show_instead] if self.deleted_at.present?
      self.read_attribute options[:field_to_hide].to_sym
    end
  end
end

class Post < ActiveRecord::Base
  act_as_fake_deletable

class Book < ActiveRecord::Base
  act_as_fake_deletable field_to_hide: :title, message_to_show_instead: "This book has been deleted man, sorry!"