Adds first extension, coercion, road to 2.0 begins.

1 files changed, 101 insertions, 0 deletions

diff --git a/lib/hashie/extensions/coercion.rb b/lib/hashie/extensions/coercion.rb
new file mode 100644
index 0000000..848abe1
--- /dev/null
+++ b/lib/hashie/extensions/coercion.rb
@@ -0,0 +1,101 @@
+module Hashie
+  module Extensions
+    module Coercion
+      def self.included(base)
+        base.send :extend, ClassMethods
+        base.send :include, InstanceMethods
+      end
+
+      module InstanceMethods
+        def []=(key, value)
+          into = self.class.key_coercion(key) || self.class.value_coercion(value)
+
+          if value && into
+            if into.respond_to?(:coerce)
+              value = into.coerce(value)
+            else
+              value = into.new(value)
+            end
+          end
+
+          super(key, value)
+        end
+      end
+
+      module ClassMethods
+        # Set up a coercion rule such that any time the specified
+        # key is set it will be coerced into the specified class.
+        # Coercion will occur by first attempting to call Class.coerce 
+        # and then by calling Class.new with the value as an argument
+        # in either case.
+        #
+        # @param [Object] key the key you would like to be coerced.
+        # @param [Class] into the class into which you want the key coerced.
+        #
+        # @example Coerce a "user" subhash into a User object
+        #   class Tweet < Hash
+        #     include Hashie::Extensions::Coercion
+        #     coerce_key :user, User
+        #   end
+        def coerce_key(key, into)
+          (@key_coercions ||= {})[key] = into
+        end
+
+        # Returns a hash of any existing key coercions.
+        def key_coercions
+          @key_coercions || {}
+        end
+
+        # Returns the specific key coercion for the specified key,
+        # if one exists.
+        def key_coercion(key)
+          key_coercions[key]
+        end
+
+        # Set up a coercion rule such that any time a value of the
+        # specified type is set it will be coerced into the specified
+        # class.
+        #
+        # @param [Class] from the type you would like coerced.
+        # @param [Class] into the class into which you would like the value coerced.
+        # @option options [Boolean] :strict (true) whether use exact source class only or include ancestors
+        #
+        # @example Coerce all hashes into this special type of hash
+        #   class SpecialHash < Hash
+        #     include Hashie::Extensions::Coercion
+        #     coerce_value Hash, SpecialHash
+        #
+        #     def initialize(hash = {})
+        #       super
+        #       hash.each_pair do |k,v|
+        #         self[k] = v
+        #       end
+        #     end
+        #   end
+        def coerce_value(from, into, options = {})
+          options = {:strict => true}.merge(options)
+
+          if options[:strict]
+            (@strict_value_coercions ||= {})[from] = into
+          else
+            while from.superclass && from.superclass != Object
+              (@lenient_value_coercions ||= {})[from] = into
+              from = from.superclass
+            end
+          end
+        end
+        
+        # Return all value coercions that have the :strict rule as true.
+        def strict_value_coercions; @strict_value_coercions || {} end
+        # Return all value coercions that have the :strict rule as false.
+        def lenient_value_coercions; @value_coercions || {} end
+
+        # Fetch the value coercion, if any, for the specified object.
+        def value_coercion(value)
+          from = value.class
+          strict_value_coercions[from] || lenient_value_coercions[from] 
+        end
+      end
+    end
+  end
+end