Added support for scoped slugs using multiple columns

lib/friendly_id/scoped.rb

@@ -105,27 +105,27 @@ module Configuration
       # @return Symbol The scope value
       attr_accessor :scope
 
-      # Gets the scope column.
+      # Gets the scope columns.
       #
       # Checks to see if the +:scope+ option passed to
       # {FriendlyId::Base#friendly_id} refers to a relation, and if so, returns
       # the realtion's foreign key. Otherwise it assumes the option value was
       # the name of column and returns it cast to a String.
       #
       # @return String The scope column
-      def scope_column
-        (reflection_foreign_key or @scope).to_s
+      def scope_columns
+        [@scope].flatten.map { |s| (reflection_foreign_key(s) or s).to_s }
       end
 
       private
 
       if ActiveRecord::VERSION::STRING < "3.1"
-        def reflection_foreign_key
-          model_class.reflections[@scope].try(:primary_key_name)
+        def reflection_foreign_key(scope)
+          model_class.reflections[scope].try(:primary_key_name)
         end
       else
-        def reflection_foreign_key
-          model_class.reflections[@scope].try(:foreign_key)
+        def reflection_foreign_key(scope)
+          model_class.reflections[scope].try(:foreign_key)
         end
       end
     end
@@ -137,8 +137,12 @@ module SlugGenerator
       private
 
       def conflict
-        column = friendly_id_config.scope_column
-        conflicts.where(column => sluggable.send(column)).first
+        columns = friendly_id_config.scope_columns
+        matched = columns.inject(conflicts) do |memo, column|
+           memo.where(column => sluggable.send(column))
+        end
+
+        matched.first
       end
     end
   end

test/schema.rb

@@ -30,6 +30,7 @@ def up
 
           # This will be used to test scopes
           add_column :novels, :novelist_id, :integer
+          add_column :novels, :publisher_id, :integer
           remove_index :novels, :slug
 
           # This will be used to test column name quoting
@@ -53,7 +54,7 @@ def slugged_tables
         end
 
         def simple_tables
-          ["authors", "books"]
+          ["authors", "books", "publishers"]
         end
 
         def tables
@@ -62,4 +63,4 @@ def tables
       end
     end
   end
-end
+end

test/scoped_test.rb

@@ -8,7 +8,12 @@ class Novelist < ActiveRecord::Base
 class Novel < ActiveRecord::Base
   extend FriendlyId
   belongs_to :novelist
-  friendly_id :name, :use => :scoped, :scope => :novelist
+  belongs_to :publisher
+  friendly_id :name, :use => :scoped, :scope => [:publisher, :novelist]
+end
+
+class Publisher < ActiveRecord::Base
+  has_many :novels
 end
 
 class ScopedTest < MiniTest::Unit::TestCase
@@ -21,7 +26,7 @@ def model_class
   end
 
   test "should detect scope column from belongs_to relation" do
-    assert_equal "novelist_id", Novel.friendly_id_config.scope_column
+    assert_equal ["publisher_id", "novelist_id"], Novel.friendly_id_config.scope_columns
   end
 
   test "should detect scope column from explicit column name" do
@@ -30,7 +35,7 @@ def model_class
       extend FriendlyId
       friendly_id :empty, :use => :scoped, :scope => :dummy
     end
-    assert_equal "dummy", model_class.friendly_id_config.scope_column
+    assert_equal ["dummy"], model_class.friendly_id_config.scope_columns
   end
 
   test "should allow duplicate slugs outside scope" do
@@ -59,4 +64,20 @@ def model_class
       model_class.friendly_id :name, :use => [:scoped, :history]
     end
   end
-end
+
+  test "should apply scope with multiple columns" do
+    transaction do
+      novelist = Novelist.create! :name => "a"
+      publisher = Publisher.create! :name => "b"
+
+      novel1 = Novel.create! :name => "c", :novelist => novelist, :publisher => publisher
+      novel2 = Novel.create! :name => "c", :novelist => novelist, :publisher => Publisher.create(:name => "d")
+      novel3 = Novel.create! :name => "c", :novelist => Novelist.create(:name => "e"), :publisher => publisher
+      novel4 = Novel.create! :name => "c", :novelist => novelist, :publisher => publisher
+
+      assert_equal novel1.friendly_id, novel2.friendly_id
+      assert_equal novel2.friendly_id, novel3.friendly_id
+      assert novel3.friendly_id != novel4.friendly_id
+    end
+  end
+end