add praises count to library

app/models/library.rb

@@ -10,6 +10,8 @@ class Library < ApplicationRecord
 
   has_many :attachments, as: :container
   has_one :praise_tread_cache, foreign_key: :object_id
+  has_many :praise_treads, as: :praise_tread_object, dependent: :destroy
+
 
   validates :uuid, presence: true, uniqueness: true
 

db/migrate/20190801084533_add_praises_count_to_libraries.rb

@@ -0,0 +1,10 @@
+class AddPraisesCountToLibraries < ActiveRecord::Migration[5.2]
+  def change
+    add_column :libraries, :praises_count, :integer, :default => 0
+
+    Library.find_each do |library|
+      praises_count = library.praise_treads.count
+      library.update_column(:praises_count, praises_count)
+    end
+  end
+end