close #184

app/models/concerns/with_slug.rb

@@ -2,6 +2,7 @@ module WithSlug
   extend ActiveSupport::Concern
 
   included do
+    validates :slug, presence: true
     validate :slug_must_be_unique
     validates :slug, format: { with: /\A[a-z0-9\-]+\z/, message: I18n.t('slug_error') }
 

app/models/research/journal/article.rb

@@ -37,6 +37,7 @@ class Research::Journal::Article < ApplicationRecord
   include WithGit
   include WithBlobs
   include WithPosition
+  include WithSlug
 
   has_summernote :text
   has_one_attached :pdf

app/models/research/journal/volume.rb

@@ -28,8 +28,9 @@
 #
 class Research::Journal::Volume < ApplicationRecord
   include WithGit
-  include WithFeaturedImage
   include WithBlobs
+  include WithFeaturedImage
+  include WithSlug
 
   belongs_to :university
   belongs_to :journal, foreign_key: :research_journal_id