to_sql visitor started

lib/arel.rb

@@ -2,6 +2,7 @@ require 'arel/version'
 require 'arel/table'
 require 'arel/attributes'
 require 'arel/nodes'
+require 'arel/visitors/to_sql'
 
 # below is deprecated
 require 'arel/sql/engine'

lib/arel/nodes/equality.rb

@@ -7,6 +7,11 @@ module Arel
         @left  = left
         @right = right
       end
+
+      def to_sql
+        viz = Visitors::ToSql.new left.relation.engine
+        viz.accept self
+      end
     end
   end
 end

lib/arel/table.rb

@@ -3,6 +3,8 @@ module Arel
     @engine = nil
     class << self; attr_accessor :engine; end
 
+    attr_reader :name, :engine
+
     def initialize name, engine = Table.engine
       @name   = name
       @engine = engine

lib/arel/visitors/to_sql.rb

@@ -0,0 +1,38 @@
+module Arel
+  module Visitors
+    class ToSql
+      def initialize engine
+        @engine     = engine
+        @connection = nil
+      end
+
+      def accept object
+        @connection = @engine.connection
+        visit object
+      end
+
+      private
+      def visit_Arel_Nodes_Equality o
+        "#{visit o.left} = #{visit o.right}"
+      end
+
+      def visit_Arel_Attributes_Integer o
+        "#{quote_table_name o.relation.name}.#{quote_column_name o.name}"
+      end
+
+      def visit_Fixnum o; o end
+
+      def visit object
+        send :"visit_#{object.class.name.gsub('::', '_')}", object
+      end
+
+      def quote_table_name name
+        @connection.quote_table_name name
+      end
+
+      def quote_column_name name
+        @connection.quote_column_name name
+      end
+    end
+  end
+end

spec/arel/attributes/attribute_spec.rb

@@ -13,5 +13,15 @@ module Arel
         end
       end
     end
+
+    describe 'equality' do
+      describe '#to_sql' do
+        it 'should produce sql' do
+          table = Table.new :users
+          condition = table['id'].eq 1
+          condition.to_sql.should == '"users"."id" = 1'
+        end
+      end
+    end
   end
 end

spec/arel/table_spec.rb

@@ -14,6 +14,14 @@ module Arel
       end
     end
 
+    it "should have a name" do
+      @relation.name.should == :users
+    end
+
+    it "should have an engine" do
+      @relation.engine.should == Table.engine
+    end
+
     describe '[]' do
       describe 'when given a', Symbol do
         it "manufactures an attribute if the symbol names an attribute within the relation" do