Extract module for list of permitted params

app/api/using_grape/artworks_endpoint.rb

@@ -4,7 +4,7 @@ class ArtworksEndpoint < Grape::API
 
     helpers do
       def artwork_params
-        params.permit(:amount_cents, :artist_name, :medium, :title)
+        params.permit(*Artwork.permitted_params)
       end
     end
 

app/models/artwork.rb

@@ -4,4 +4,11 @@ class Artwork < ApplicationRecord
   validates :featured, inclusion: {in: [true, false]}
   validates :medium, presence: true
   validates :title, presence: true
+
+  include HasPermittedParams
+  has_permitted_params \
+    :amount_cents,
+    :artist_name,
+    :medium,
+    :title
 end

app/models/concerns/has_permitted_params.rb

@@ -0,0 +1,13 @@
+module HasPermittedParams
+  extend ActiveSupport::Concern
+
+  class_methods do
+    def has_permitted_params(*params)
+      @permitted_params = params
+    end
+
+    def permitted_params
+      @permitted_params
+    end
+  end
+end