From 65200d2933bd337b8347dd32502a12c2fddf24f0 Mon Sep 17 00:00:00 2001
From: Pratik Naik <pratiknaik@gmail.com>
Date: Sun, 3 Jan 2010 00:08:59 +0530
Subject: [PATCH] Implement Relation#new

---
 activerecord/lib/active_record/relation.rb | 13 ++++++++++++-
 activerecord/test/cases/relations_test.rb  | 16 ++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 6eb1d907e6..0319781e03 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -15,6 +15,10 @@ module ActiveRecord
       @loaded, @readonly = false
     end
 
+    def new(*args, &block)
+      @klass.send(:with_scope, :create => create_scope) { @klass.new(*args, &block) }
+    end
+
     def merge(r)
       raise ArgumentError, "Cannot merge a #{r.klass.name} relation with #{@klass.name} relation" if r.klass != @klass
 
@@ -138,7 +142,7 @@ module ActiveRecord
     end
 
     def reset
-      @first = @last = nil
+      @first = @last = @create_scope = nil
       @records = []
       self
     end
@@ -181,6 +185,13 @@ module ActiveRecord
       end
     end
 
+    def create_scope
+      @create_scope ||= wheres.inject({}) do |hash, where|
+        hash[where.operand1.name] = where.operand2.value if where.is_a?(Arel::Predicates::Equality)
+        hash
+      end
+    end
+
     def where_clause(join_string = " AND ")
       @relation.send(:where_clauses).join(join_string)
     end
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 6605c8bf34..c4b2c21578 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -477,4 +477,20 @@ class RelationTest < ActiveRecord::TestCase
     assert posts.many?
     assert ! posts.limit(1).many?
   end
+
+  def test_build
+    posts = Post.scoped
+
+    post = posts.new
+    assert_kind_of Post, post
+  end
+
+  def test_scoped_build
+    posts = Post.where(:title => 'You told a lie')
+
+    post = posts.new
+    assert_kind_of Post, post
+    assert_equal 'You told a lie', post.title
+  end
+
 end