obj.class_variable_defined?(symbol)    → true or false

Returns true if the given class variable is defined in obj.

class Fred
  @@foo = 99
end
Fred.class_variable_defined?(:@@foo)    #=> true
Fred.class_variable_defined?(:@@bar)    #=> false

Source Code

/*
*  call-seq:
*     obj.class_variable_defined?(symbol)    => true or false
*
*  Returns <code>true</code> if the given class variable is defined
*  in <i>obj</i>.
*
*     class Fred
*       @@foo = 99
*     end
*     Fred.class_variable_defined?(:@@foo)    #=> true
*     Fred.class_variable_defined?(:@@bar)    #=> false
*/

static VALUE
rb_mod_cvar_defined(obj, iv)
   VALUE obj, iv;
{
   ID id = rb_to_id(iv);

   if (!rb_is_class_id(id)) {
       rb_name_error(id, "`%s' is not allowed as a class variable name", rb_id2name(id));
   }
   return rb_cvar_defined(obj, id);
}