1 files changed, 88 insertions, 0 deletions
diff --git a/lib/hashie/extensions/dash/predefined_values.rb b/lib/hashie/extensions/dash/predefined_values.rb
new file mode 100644
index 0000000..2a0b7ca
--- /dev/null
+++ b/lib/hashie/extensions/dash/predefined_values.rb
@@ -0,0 +1,88 @@
+module Hashie
+  module Extensions
+    module Dash
+      # Extends a Dash with the ability to accept only predefined values on a property.
+      #
+      # == Example
+      #
+      #   class PersonHash < Hashie::Dash
+      #     include Hashie::Extensions::Dash::PredefinedValues
+      #
+      #     property :gender, values: [:male, :female, :prefer_not_to_say]
+      #     property :age, values: (0..150) # a Range
+      #   end
+      #
+      #   person = PersonHash.new(gender: :male, age: -1)
+      #   # => ArgumentError: The value '-1' is not accepted for property 'age'
+      module PredefinedValues
+        def self.included(base)
+          base.instance_variable_set(:@values_for_properties, {})
+          base.extend(ClassMethods)
+          base.include(InstanceMethods)
+        end
+
+        module ClassMethods
+          attr_reader :values_for_properties
+
+          def inherited(klass)
+            super
+            klass.instance_variable_set(:@values_for_properties, values_for_properties.dup)
+          end
+
+          def property(property_name, options = {})
+            super
+
+            return unless (predefined_values = options[:values])
+
+            assert_predefined_values!(predefined_values)
+            set_predefined_values(property_name, predefined_values)
+          end
+
+          private
+
+          def assert_predefined_values!(predefined_values)
+            return if supported_type?(predefined_values)
+
+            raise ArgumentError, %(`values` accepts an Array or a Range.)
+          end
+
+          def supported_type?(predefined_values)
+            [::Array, ::Range].any? { |klass| predefined_values.is_a?(klass) }
+          end
+
+          def set_predefined_values(property_name, predefined_values)
+            @values_for_properties[property_name] = predefined_values
+          end
+        end
+
+        module InstanceMethods
+          def initialize(*)
+            super
+
+            assert_property_values!
+          end
+
+          private
+
+          def assert_property_values!
+            self.class.values_for_properties.each_key do |property|
+              value = send(property)
+
+              if value && !values_for_properties(property).include?(value)
+                fail_property_value_error!(property)
+              end
+            end
+          end
+
+          def fail_property_value_error!(property)
+            raise ArgumentError, "Invalid value for property '#{property}'"
+          end
+
+          def values_for_properties(property)
+            self.class.values_for_properties[property]
+          end
+        end
+      end
+    end
+  end
+end