QR codes generation

app/models/contestant.rb

@@ -7,6 +7,7 @@
 #  email          :string
 #  name           :string
 #  projected_time :string
+#  qrcode         :string
 #  time_seconds   :integer
 #  created_at     :datetime         not null
 #  updated_at     :datetime         not null
@@ -27,6 +28,7 @@ class Contestant < ApplicationRecord
   has_and_belongs_to_many :categories
 
   before_validation :initialize_time_seconds_if_empty
+  before_commit :generate_qrcode, on: :create
 
   validates :name, presence: true
   validates :time_seconds, presence: true
@@ -48,4 +50,17 @@ class Contestant < ApplicationRecord
       self.time_seconds = 0
     end
   end
+
+  def generate_qrcode
+    host = Rails.application.config.action_controller.default_url_options[:host]
+    qrcode = RQRCode::QRCode.new("https://#{host}/public/p/#{self.generate_token_for(:token)}")
+    self.qrcode = qrcode.as_svg(
+      color: "000",
+      shape_rendering: "crispEdges",
+      module_size: 3,
+      standalone: true,
+      use_path: true,
+      viewbox: true
+    )
+  end
 end