remove knowledge of SQL from the column definition object

activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb

@@ -20,29 +20,9 @@ def string_to_binary(value)
         value
       end
 
-      def sql_type
-        base.type_to_sql(type.to_sym, limit, precision, scale)
-      end
-
       def primary_key?
         type.to_sym == :primary_key
       end
-
-      def to_sql
-        column_sql = "#{base.quote_column_name(name)} #{sql_type}"
-        column_options = {}
-        column_options[:null] = null unless null.nil?
-        column_options[:default] = default unless default.nil?
-        column_options[:column] = self
-        add_column_options!(column_sql, column_options) unless primary_key?
-        column_sql
-      end
-
-      private
-
-        def add_column_options!(sql, options)
-          base.add_column_options!(sql, options)
-        end
     end
 
     # Represents the schema of an SQL table in an abstract way. This class
@@ -287,7 +267,8 @@ def references(*args)
       # concatenated together. This string can then be prepended and appended to
       # to generate the final SQL to create the table.
       def to_sql
-        columns.map { |c| c.to_sql } * ', '
+        viz = @base.schema_creation
+        columns.map { |c| viz.accept c }.join ', '
       end
 
       private

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -100,6 +100,47 @@ def initialize(connection, logger = nil, pool = nil) #:nodoc:
         @visitor             = nil
       end
 
+      class SchemaCreation
+        def initialize(conn)
+          @conn  = conn
+          @cache = {}
+        end
+
+        def accept(o)
+          m = @cache[o.class] ||= "visit_#{o.class.name.split('::').last}"
+          send m, o
+        end
+
+        private
+
+        def visit_ColumnDefinition(o)
+          sql_type = type_to_sql(o.type.to_sym, o.limit, o.precision, o.scale)
+          column_sql = "#{quote_column_name(o.name)} #{sql_type}"
+          column_options = {}
+          column_options[:null] = o.null unless o.null.nil?
+          column_options[:default] = o.default unless o.default.nil?
+          column_options[:column] = o
+          add_column_options!(column_sql, column_options) unless o.primary_key?
+          column_sql
+        end
+
+        def quote_column_name(name)
+          @conn.quote_column_name name
+        end
+
+        def type_to_sql(type, limit, precision, scale)
+          @conn.type_to_sql type.to_sym, limit, precision, scale
+        end
+
+        def add_column_options!(column_sql, column_options)
+          @conn.add_column_options! column_sql, column_options
+        end
+      end
+
+      def schema_creation
+        SchemaCreation.new self
+      end
+
       def lease
         synchronize do
           unless in_use

activerecord/test/cases/column_definition_test.rb

@@ -8,6 +8,7 @@ def setup
         def @adapter.native_database_types
           {:string => "varchar"}
         end
+        @viz = @adapter.schema_creation
       end
 
       def test_can_set_coder
@@ -37,7 +38,7 @@ def test_should_not_include_default_clause_when_default_is_null
         column_def = ColumnDefinition.new(
           @adapter, column.name, "string",
           column.limit, column.precision, column.scale, column.default, column.null)
-          assert_equal "title varchar(20)", column_def.to_sql
+          assert_equal "title varchar(20)", @viz.accept(column_def)
       end
 
       def test_should_include_default_clause_when_default_is_present
@@ -45,7 +46,7 @@ def test_should_include_default_clause_when_default_is_present
         column_def = ColumnDefinition.new(
           @adapter, column.name, "string",
           column.limit, column.precision, column.scale, column.default, column.null)
-          assert_equal %Q{title varchar(20) DEFAULT 'Hello'}, column_def.to_sql
+          assert_equal %Q{title varchar(20) DEFAULT 'Hello'}, @viz.accept(column_def)
       end
 
       def test_should_specify_not_null_if_null_option_is_false
@@ -53,7 +54,7 @@ def test_should_specify_not_null_if_null_option_is_false
         column_def = ColumnDefinition.new(
           @adapter, column.name, "string",
           column.limit, column.precision, column.scale, column.default, column.null)
-          assert_equal %Q{title varchar(20) DEFAULT 'Hello' NOT NULL}, column_def.to_sql
+          assert_equal %Q{title varchar(20) DEFAULT 'Hello' NOT NULL}, @viz.accept(column_def)
       end
 
       if current_adapter?(:MysqlAdapter)