* object.c (rb_obj_singleton_class): new method

Kernel#singleton_class.  [ruby-core:21702]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27022 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Tue Mar 23 18:35:46 2010  Shugo Maeda  <shugo@ruby-lang.org>
+
+	* object.c (rb_obj_singleton_class): new method
+	  Kernel#singleton_class.  [ruby-core:21702]
+
 Tue Mar 23 01:13:59 2010  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket: use rsock_ prefix for internal initialization functions.

object.c

@@ -162,6 +162,29 @@ rb_obj_class(VALUE obj)
     return rb_class_real(CLASS_OF(obj));
 }
 
+/*
+ *  call-seq:
+ *     obj.singleton_class    => class
+ *
+ *  Returns the singleton class of <i>obj</i>.  This method creates
+ *  a new singleton class if <i>obj</i> does not have it.
+ *
+ *  If <i>obj</i> is <code>nil</code>, <code>true</code>, or
+ *  <code>false</code>, it returns NilClass, TrueClass, or FalseClass,
+ *  respectively.
+ *  If <i>obj</i> is a Fixnum or a Symbol, it raises a TypeError.
+ *
+ *     Object.new.singleton_class  #=> #<Class:#<Object:0xb7ce1e24>>
+ *     String.singleton_class      #=> #<Class:String>
+ *     nil.singleton_class         #=> NilClass
+ */
+
+static VALUE
+rb_obj_singleton_class(VALUE obj)
+{
+    return rb_singleton_class(obj);
+}
+
 static void
 init_copy(VALUE dest, VALUE obj)
 {
@@ -2585,6 +2608,7 @@ Init_Object(void)
     rb_define_method(rb_mKernel, "<=>", rb_obj_cmp, 1);
 
     rb_define_method(rb_mKernel, "class", rb_obj_class, 0);
+    rb_define_method(rb_mKernel, "singleton_class", rb_obj_singleton_class, 0);
     rb_define_method(rb_mKernel, "clone", rb_obj_clone, 0);
     rb_define_method(rb_mKernel, "dup", rb_obj_dup, 0);
     rb_define_method(rb_mKernel, "initialize_copy", rb_obj_init_copy, 1);

test/ruby/test_object.rb

@@ -561,4 +561,25 @@ class TestObject < Test::Unit::TestCase
       end
     end.call
   end
+
+  def test_singleton_class
+    x = Object.new
+    xs = class << x; self; end
+    assert_equal(xs, x.singleton_class)
+
+    y = Object.new
+    ys = y.singleton_class
+    assert_equal(class << y; self; end, ys)
+
+    assert_equal(NilClass, nil.singleton_class)
+    assert_equal(TrueClass, true.singleton_class)
+    assert_equal(FalseClass, false.singleton_class)
+
+    assert_raise(TypeError) do
+      123.singleton_class
+    end
+    assert_raise(TypeError) do
+      :foo.singleton_class
+    end
+  end
 end