New logic to counter service

app/controllers/api/shelvings_controller.rb

@@ -8,7 +8,7 @@ def index
 
   def create
     shelving = @bookshelf.shelvings.new(shelving_params)
-    Bookshelf.change_count('inc', @bookshelf)
+    Bookshelves::BookshelfShelvingCounter.new('inc', @bookshelf).change_count
     if shelving.save
       render json: shelving
     else
@@ -31,8 +31,9 @@ def update
 
   def destroy
     shelving = Shelving.find(params[:id].to_i)
+    bookshelf = Bookshelves::BookshelfShelvingCounter.new('dec', @bookshelf).change_count
     if shelving.destroy
-      render json: Bookshelf.change_count('dec', @bookshelf)
+      render json: bookshelf
     else
       render json: { errors: shelf.errors.full_messages.join(', ')}, status: 422
     end

app/models/book.rb

@@ -20,18 +20,9 @@ def self.check_if_duplicate(book_params)
 
   def self.only_with_ratings
     distinct.select('books.item, r.book_id, COUNT(r.book_id) AS review_count, AVG(r.value)')
-    .joins('INNER JOIN ratings AS r ON books.id = r.book_id')
-    .group('r.book_id, books.item')
-    .order('avg DESC')
-    .limit('20')
-  end
-
-  def self.change_count(action, bookshelf)
-    case action
-      when 'inc'
-        bookshelf.update(book_count: bookshelf.book_count += 1)
-      when 'dec'
-        bookshelf.update(book_count: bookshelf.book_count -= 1)
-    end
+      .joins('INNER JOIN ratings AS r ON books.id = r.book_id')
+      .group('r.book_id, books.item')
+      .order('avg DESC')
+      .limit('20')
   end
 end

app/services/bookshelves/bookshelf_shelving_counter.rb

@@ -0,0 +1,20 @@
+module Bookshelves
+  class BookshelfShelvingCounter
+    def initialize(action, bookshelf)
+      @action = action
+      @bookshelf = bookshelf
+    end
+
+    attr_accessor :action, :bookshelf
+
+    def change_count
+      case action
+      when 'inc'
+        bookshelf.update(book_count: bookshelf.book_count += 1)
+      when 'dec'
+        bookshelf.update(book_count: bookshelf.book_count -= 1)
+      end
+      bookshelf
+    end
+  end
+end