implement inverse_of validator

lib/goo/validators/enforce.rb

@@ -45,6 +45,8 @@ def enforce(inst,attr,value)
               check Goo::Validators::DistinctOf, inst, attr, value, opt, opt
             when /^superior_equal_to_/
               check Goo::Validators::SuperiorEqualTo, inst, attr, value, opt, opt
+            when /^inverse_of_/
+              check Goo::Validators::InverseOf, inst, attr, value, opt, opt
             when Proc
               call_proc(opt, inst, attr)
             when /^max_/, /^min_/

lib/goo/validators/implementations/inverse_of.rb

@@ -0,0 +1,35 @@
+module Goo
+  module Validators
+    class InverseOf < ValidatorBase
+      include Validator
+
+      key :inverse_of_
+
+      error_message ->(obj) {
+        "`#{@attr}` must be the inverse of ``#{@property}``"
+      }
+
+      validity_check -> (obj) do
+        return true if self.class.empty_value?(@value)
+
+        return Array(@value).select{|x| not inverse?(@property,x, @inst)}.empty?
+      end
+
+      def initialize(inst, attr, value, key)
+        super(inst, attr, value)
+        @property = self.class.property(key)
+      end
+
+      def inverse?(attr, value, source_object)
+        if self.class.respond_to?(attr, value)
+          target_values = self.class.attr_value(attr, value)
+          return target_values.any?{ |target_object| self.class.equivalent_value?(target_object, source_object)}
+        end
+
+        false
+      end
+
+
+    end
+  end
+end

lib/goo/validators/validator.rb

@@ -61,6 +61,11 @@ def property(key)
           key[ids.first.size..key.size].to_sym
         end
 
+        def respond_to?(attr, object)
+          object && object.respond_to?(attr)
+        end
+
+
         def equivalent_value?(object1, object2)
           if object1.respond_to?(:id) && object2.respond_to?(:id)
             object1.id.eql?(object2.id)