added attribute.eq(nil)

  - produces attribute IS NULL

8 files changed, 19 insertions, 7 deletions

diff --git a/lib/active_relation/extensions.rb b/lib/active_relation/extensions.rb
index 21d6724004..ded830eb8c 100644
--- a/lib/active_relation/extensions.rb
+++ b/lib/active_relation/extensions.rb
@@ -2,4 +2,5 @@ require 'active_relation/extensions/object'
 require 'active_relation/extensions/class'
 require 'active_relation/extensions/array'
 require 'active_relation/extensions/hash'
-require 'active_relation/extensions/range'
\ No newline at end of file
+require 'active_relation/extensions/range'
+require 'active_relation/extensions/nil_class'
\ No newline at end of file
diff --git a/lib/active_relation/extensions/array.rb b/lib/active_relation/extensions/array.rb
index 2af5832707..793c06aad8 100644
--- a/lib/active_relation/extensions/array.rb
+++ b/lib/active_relation/extensions/array.rb
@@ -7,7 +7,7 @@ class Array
     "(" + collect { |e| e.to_sql(formatter) }.join(', ') + ")"
   end
   
-  def predicate_sql
+  def inclusion_predicate_sql
     "IN"
   end
 end
\ No newline at end of file
diff --git a/lib/active_relation/extensions/nil_class.rb b/lib/active_relation/extensions/nil_class.rb
new file mode 100644
index 0000000000..729c4cada7
--- /dev/null
+++ b/lib/active_relation/extensions/nil_class.rb
@@ -0,0 +1,5 @@
+class NilClass
+  def equality_predicate_sql
+    'IS'
+  end
+end
\ No newline at end of file
diff --git a/lib/active_relation/extensions/object.rb b/lib/active_relation/extensions/object.rb
index cd51543c91..25cef989a4 100644
--- a/lib/active_relation/extensions/object.rb
+++ b/lib/active_relation/extensions/object.rb
@@ -7,6 +7,10 @@ class Object
     formatter.scalar self
   end
   
+  def equality_predicate_sql
+    '='
+  end
+  
   def metaclass
     class << self
       self
diff --git a/lib/active_relation/extensions/range.rb b/lib/active_relation/extensions/range.rb
index 0218a0ab44..d7329efe34 100644
--- a/lib/active_relation/extensions/range.rb
+++ b/lib/active_relation/extensions/range.rb
@@ -3,7 +3,7 @@ class Range
     formatter.range self.begin, self.end
   end
   
-  def predicate_sql
+  def inclusion_predicate_sql
     "BETWEEN"
   end
 end
\ No newline at end of file
diff --git a/lib/active_relation/predicates.rb b/lib/active_relation/predicates.rb
index 6fcef3cfd6..22fbcd9f0b 100644
--- a/lib/active_relation/predicates.rb
+++ b/lib/active_relation/predicates.rb
@@ -41,7 +41,7 @@ module ActiveRelation
     end
 
     def predicate_sql
-      '='
+      operand2.equality_predicate_sql
     end
   end
 
@@ -74,6 +74,8 @@ module ActiveRelation
   end
   
   class In < Binary
-    delegate :predicate_sql, :to => :operand2
+    def predicate_sql
+      operand2.inclusion_predicate_sql
+    end
   end
 end
\ No newline at end of file
diff --git a/lib/active_relation/primitives/value.rb b/lib/active_relation/primitives/value.rb
index aeee89dc3b..6f251d442b 100644
--- a/lib/active_relation/primitives/value.rb
+++ b/lib/active_relation/primitives/value.rb
@@ -2,7 +2,7 @@ module ActiveRelation
   class Value
     attr_reader :value, :relation
     
-    delegate :predicate_sql, :to => :value
+    delegate :inclusion_predicate_sql, :equality_predicate_sql, :to => :value
     
     def initialize(value, relation)
       @value, @relation = value, relation
diff --git a/lib/active_relation/relations/relation.rb b/lib/active_relation/relations/relation.rb
index 88d1bce4a8..db61fce3de 100644
--- a/lib/active_relation/relations/relation.rb
+++ b/lib/active_relation/relations/relation.rb
@@ -115,7 +115,7 @@ module ActiveRelation
     end
     alias_method :to_s, :to_sql
     
-    def predicate_sql
+    def inclusion_predicate_sql
       "IN"
     end