custom primary key for transaction

app/models/sale_item.rb

@@ -1,9 +1,15 @@
 class SaleItem < ApplicationRecord
-#primary key - need to be unique generated for multiple shops
+  #primary key - need to be unique generated for multiple shops
+  before_create :generate_custom_id
 
   belongs_to :sale
 
   #compute items - discount, tax, price_change
   def compute_item
   end
+
+  private
+  def generate_custom_id
+    self.sale_item_id = SeedGenerator.generate_id(self.class.name, "SLI")
+  end
 end