use Session.instance rather than Session.new for easier code

4 files changed, 21 insertions, 37 deletions

diff --git a/lib/arel/algebra/relations/relation.rb b/lib/arel/algebra/relations/relation.rb
index 0332482066..34181beea2 100644
--- a/lib/arel/algebra/relations/relation.rb
+++ b/lib/arel/algebra/relations/relation.rb
@@ -3,7 +3,7 @@ module Arel
     attr_reader :count
 
     def session
-      Session.new
+      Session.instance
     end
 
     def call
diff --git a/lib/arel/session.rb b/lib/arel/session.rb
index e6da825b97..622ca090f8 100644
--- a/lib/arel/session.rb
+++ b/lib/arel/session.rb
@@ -1,30 +1,14 @@
 module Arel
   class Session
-    class << self
-      attr_accessor :instance
-      alias_method :manufacture, :new
+    def self.instance
+      @instance || new
+    end
 
-      def start
-        if defined?(@started) && @started
-          yield
-        else
-          begin
-            @started = true
-            @instance = manufacture
-            singleton_class.class_eval do
-              undef :new
-              alias_method :new, :instance
-            end
-            yield
-          ensure
-            singleton_class.class_eval do
-              undef :new
-              alias_method :new, :manufacture
-            end
-            @started = false
-          end
-        end
-      end
+    def self.start
+      @instance ||= new
+      yield @instance
+    ensure
+      @instance = nil
     end
 
     module CRUD
diff --git a/spec/algebra/unit/relations/relation_spec.rb b/spec/algebra/unit/relations/relation_spec.rb
index a1d1793d92..be77c64b17 100644
--- a/spec/algebra/unit/relations/relation_spec.rb
+++ b/spec/algebra/unit/relations/relation_spec.rb
@@ -148,8 +148,8 @@ module Arel
       describe Relation::Operable::Writable do
         describe '#delete' do
           it 'manufactures a deletion relation' do
-            Session.start do
-              Session.new.should_receive(:delete).with(Deletion.new(@relation))
+            Session.start do |s|
+              s.should_receive(:delete).with(Deletion.new(@relation))
               @relation.delete
             end
           end
@@ -157,9 +157,9 @@ module Arel
 
         describe '#insert' do
           it 'manufactures an insertion relation' do
-            Session.start do
+            Session.start do |s|
               record = { @relation[:name] => 'carl' }
-              Session.new.should_receive(:create).with(Insert.new(@relation, record))
+              s.should_receive(:create).with(Insert.new(@relation, record))
               @relation.insert(record)
             end
           end
@@ -167,9 +167,9 @@ module Arel
 
         describe '#update' do
           it 'manufactures an update relation' do
-            Session.start do
+            Session.start do |s|
               assignments = { @relation[:name] => Value.new('bob', @relation) }
-              Session.new.should_receive(:update).with(Update.new(@relation, assignments))
+              s.should_receive(:update).with(Update.new(@relation, assignments))
               @relation.update(assignments)
             end
           end
diff --git a/spec/algebra/unit/session/session_spec.rb b/spec/algebra/unit/session/session_spec.rb
index 0553a140ec..421e3e3637 100644
--- a/spec/algebra/unit/session/session_spec.rb
+++ b/spec/algebra/unit/session/session_spec.rb
@@ -10,16 +10,16 @@ module Arel
     describe '::start' do
       describe '::instance' do
         it "it is a singleton within the started session" do
-          Session.start do
-            Session.new.should == Session.new
+          Session.start do |session|
+            Session.instance.should == session
           end
         end
 
         it "is a singleton across nested sessions" do
-          Session.start do
-            outside = Session.new
-            Session.start do
-              Session.new.should == outside
+          Session.start do |s1|
+            outside = Session.instance
+            Session.start do |s2|
+              Session.instance.should == outside
             end
           end
         end