A bit of untested unfinished work on structure.

1 files changed, 47 insertions, 0 deletions

diff --git a/lib/hashie/extensions/structure.rb b/lib/hashie/extensions/structure.rb
new file mode 100644
index 0000000..adb776b
--- /dev/null
+++ b/lib/hashie/extensions/structure.rb
@@ -0,0 +1,47 @@
+module Hashie
+  module Extensions
+    # The Structure extension provides facilities for declaring
+    # properties that a Hash can have. This provides for the
+    # creation of structures that still behave like hashes but
+    # do not allow setting non-allowed keys.
+    #
+    # @example
+    #   class RestrictedHash < Hash
+    #     include Hashie::Extensions::MergeInitializer
+    #     include Hashie::Extensions::Structure
+    #
+    #     key :first
+    #     key :second, :default => 'foo'
+    #   end
+    #
+    #   h = RestrictedHash.new(:first => 1)
+    #   h[:first]  # => 1
+    #   h[:second] # => 'foo'
+    #   h[:third]  # => ArgumentError
+    #
+    module Structure
+      def self.included(base)
+        base.extend ClassMethods
+        base.class_eval do
+          @permitted_keys = superclass.permitted_keys if superclass.respond_to?(:permitted_keys)
+        end
+      end
+
+      module ClassMethods
+        def key(key, options = {})
+          (@permitted_keys ||= []) << key
+
+          if options[:default]
+            (@default_values ||= {})[key] = options.delete(:default)
+          end
+
+          permitted_keys
+        end
+
+        def permitted_keys
+          @permitted_keys
+        end
+      end
+    end
+  end
+end