evansharp · November 26, 2013 18:04 · Sep 25, 2012
diff --git a/random_attribute.rb b/random_attribute.rb
@@ -0,0 +1,31 @@
+module RandomAttribute
+
+  def generate_unique_random_base64(attribute, n)
+    until random_is_unique?(attribute)
+      self.send(:"#{attribute}=", random_base64(n))
+    end
+  end
+
+  def generate_unique_random_hex(attribute, n)
+    until random_is_unique?(attribute)
+      self.send(:"#{attribute}=", SecureRandom.hex(n/2))
+    end
+  end
+
+  private
+
+  def random_is_unique?(attribute)
+    val = self.send(:"#{attribute}")
+    val && !self.class.send(:"find_by_#{attribute}", val)
+  end
+
+  def random_base64(n)
+    val = base64_url
+    val += base64_url while val.length < n
+    val.slice(0..(n-1))
+  end
+
+  def base64_url
+    SecureRandom.base64(60).downcase.gsub(/\W/, '')
+  end
+end
diff --git a/user.rb b/user.rb
@@ -0,0 +1,11 @@
+class Post < ActiveRecord::Base
+
+  include RandomAttribute
+  before_validation :generate_key, on: :create
+
+  private
+
+  def generate_key
+    generate_unique_random_hex(:key, 32)
+  end
+end