implement object_type validator with the new DSL

lib/goo/validators/implementations/object_type.rb

@@ -0,0 +1,46 @@
+module Goo
+  module Validators
+    class ObjectType < ValidatorBase
+      include Validator
+
+      key :object_type
+
+      error_message ->(obj) {
+        if @error.eql?(:persistence)
+          "`#{@attr}` contains non persistent models. It will not save."
+        else
+          "`#{@attr}` contains values that are not instance of `#{@model_range.model_name}`"
+        end
+      }
+
+      validity_check -> (obj) do
+        values = Array(@value)
+
+        unless values.select { |v| !self.class.is_a_model?(v, @model_range) }.empty?
+          @error = :no_range
+          return false
+        end
+
+        unless values.select { |v| !self.class.persistent?(v) }.empty?
+          @error = :persistence
+          return false
+        end
+
+        return true
+      end
+
+      def initialize(inst, attr, value, model_range)
+        super(inst, attr, value)
+        @model_range = model_range
+      end
+
+      def self.is_a_model?(value, model_range)
+        value.is_a?(model_range) || (value.respond_to?(:klass) && value[:klass] == model_range)
+      end
+
+      def self.persistent?(value)
+        value.respond_to?(:klass) || value.persistent?
+      end
+    end
+  end
+end