Add AR::Base.to_param for convenient "pretty" URLs derived from a model's attribute or method.

activerecord/CHANGELOG.md

@@ -1,3 +1,17 @@
+*   Added `ActiveRecord::Base.to_param` for convenient "pretty" URLs derived from a model's attribute or method.
+
+    Example:
+
+      class User < ActiveRecord::Base
+        to_param :name
+      end
+
+      user = User.find_by(name: 'Fancy Pants')
+      user.id       # => 123
+      user.to_param # => "123-fancy-pants"
+
+    *Javan Makhmali*
+
 *   Added `ActiveRecord::Base.no_touching`, which allows ignoring touch on models.
 
     Examples:

activerecord/lib/active_record/integration.rb

@@ -1,3 +1,5 @@
+require 'active_support/core_ext/string/filters'
+
 module ActiveRecord
   module Integration
     extend ActiveSupport::Concern
@@ -65,5 +67,34 @@ module ActiveRecord
         "#{self.class.model_name.cache_key}/#{id}"
       end
     end
+
+    module ClassMethods
+      # Defines your model's +to_param+ method to generate "pretty" URLs
+      # using +method_name+, which can be any attribute or method that
+      # responds to +to_s+.
+      #
+      #   class User < ActiveRecord::Base
+      #     to_param :name
+      #   end
+      #
+      #   user = User.find_by(name: 'Fancy Pants')
+      #   user.id         # => 123
+      #   user_path(user) # => "/users/123-fancy-pants"
+      #
+      # Because the generated param begins with the record's +id+, it is
+      # suitable for passing to +find+. In a controller, for example:
+      #
+      #   params[:id]               # => "123-fancy-pants"
+      #   User.find(params[:id]).id # => 123
+      def to_param(method_name)
+        define_method :to_param do
+          if (default = super()) && (result = send(method_name).to_s).present?
+            "#{default}-#{result.truncate(20, separator: /\s/, omission: nil).parameterize}"
+          else
+            default
+          end
+        end
+      end
+    end
   end
 end

activerecord/test/cases/integration_test.rb

@@ -23,6 +23,24 @@ class IntegrationTest < ActiveRecord::TestCase
     assert_equal '1', client.to_param
   end
 
+  def test_to_param_class_method
+    firm = Firm.find(4)
+    assert_equal '4-flamboyant-software', firm.to_param
+  end
+
+  def to_param_class_method_uses_default_if_blank
+    firm = Firm.find(4)
+    firm.name = nil
+    assert_equal '4', firm.to_param
+    firm.name = ' '
+    assert_equal '4', firm.to_param
+  end
+
+  def to_param_class_method_uses_default_if_not_persisted
+    firm = Firm.new(name: 'Fancy Shirts')
+    assert_equal nil, firm.to_param
+  end
+
   def test_cache_key_for_existing_record_is_not_timezone_dependent
     utc_key = Developer.first.cache_key
 

activerecord/test/models/company.rb

@@ -40,6 +40,8 @@ module Namespaced
 end
 
 class Firm < Company
+  to_param :name
+
   has_many :clients, -> { order "id" }, :dependent => :destroy, :before_remove => :log_before_remove, :after_remove  => :log_after_remove
   has_many :unsorted_clients, :class_name => "Client"
   has_many :unsorted_clients_with_symbol, :class_name => :Client