From https://once.com/writebook

app/models/book/accessable.rb

@@ -0,0 +1,47 @@
+module Book::Accessable
+  extend ActiveSupport::Concern
+
+  included do
+    has_many :accesses, dependent: :destroy
+    scope :with_everyone_access, -> { where(everyone_access: true) }
+  end
+
+  class_methods do
+    def accessable_or_published(user: Current.user)
+      if user.present?
+        accessable_or_published_books
+      else
+        published
+      end
+    end
+
+    def accessable_or_published_books(user: Current.user)
+      user.books.or(published).distinct
+    end
+  end
+
+  def accessable?(user: Current.user)
+    accesses.exists?(user: user)
+  end
+
+  def editable?(user: Current.user)
+    access_for(user: user)&.editor? || user&.administrator?
+  end
+
+  def access_for(user: Current.user)
+    accesses.find_by(user: user)
+  end
+
+  def update_access(editors:, readers:)
+    editors = Set.new(editors)
+    readers = Set.new(everyone_access? ? User.active.ids : readers)
+
+    all = editors + readers
+    all_accesses = all.collect { |user_id|
+      { user_id: user_id, level: editors.include?(user_id) ? :editor : :reader }
+    }
+
+    accesses.upsert_all(all_accesses, unique_by: [ :book_id, :user_id ])
+    accesses.where.not(user_id: all).delete_all
+  end
+end

app/models/book/sluggable.rb

@@ -0,0 +1,11 @@
+module Book::Sluggable
+  extend ActiveSupport::Concern
+
+  included do
+    before_save :generate_slug, if: -> { slug.blank? }
+  end
+
+  def generate_slug
+    self.slug = title.parameterize
+  end
+end