added attribute.eq(nil)

- produces attribute IS NULL

TODO

@@ -1,8 +1,8 @@
 todo:
 - string passthrough:
  :joins=>"INNER JOIN posts ON comments.post_id = posts.id"
- :select=>"`comments`.*"
-
+   - shit this one is hard at the moment.
+   
 - need adapters for this form:
  {:conditions=>["approved = ?", false]}
  {:conditions=>{:approved=>false}}

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'
+require 'active_relation/extensions/range'
+require 'active_relation/extensions/nil_class'

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

lib/active_relation/extensions/nil_class.rb

@@ -0,0 +1,5 @@
+class NilClass
+  def equality_predicate_sql
+    'IS'
+  end
+end

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

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

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

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

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
     

spec/active_relation/unit/predicates/equality_spec.rb

@@ -5,8 +5,8 @@ module ActiveRelation
     before do
       @relation1 = Table.new(:users)
       @relation2 = Table.new(:photos)
-      @attribute1 = @relation1[:name]
-      @attribute2 = @relation2[:name]
+      @attribute1 = @relation1[:id]
+      @attribute2 = @relation2[:user_id]
     end
   
     describe '==' do 
@@ -23,5 +23,27 @@ module ActiveRelation
         Equality.new(@attribute1, @attribute2).should == Equality.new(@attribute2, @attribute1)
       end
     end
+    
+    describe '#to_sql' do
+      describe 'when relating to a non-nil value' do
+        it "manufactures an equality predicate" do
+          Equality.new(@attribute1, @attribute2).to_sql.should be_like("
+            `users`.`id` = `photos`.`user_id`
+          ")
+        end
+      end
+      
+      describe 'when relation to a nil value' do
+        before do
+          @nil = nil.bind(@relation1)
+        end
+        
+        it "manufactures an is null predicate" do
+          Equality.new(@attribute1, @nil).to_sql.should be_like("
+            `users`.`id` IS NULL
+          ")
+        end
+      end
+    end
   end
 end