1 files changed, 104 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/type/value.rb b/activemodel/lib/active_model/type/value.rb
new file mode 100644
index 0000000000..c7d1197d69
--- /dev/null
+++ b/activemodel/lib/active_model/type/value.rb
@@ -0,0 +1,104 @@
+module ActiveModel
+  module Type
+    class Value
+      attr_reader :precision, :scale, :limit
+
+      def initialize(precision: nil, limit: nil, scale: nil)
+        @precision = precision
+        @scale = scale
+        @limit = limit
+      end
+
+      def type # :nodoc:
+      end
+
+      # Converts a value from database input to the appropriate ruby type. The
+      # return value of this method will be returned from
+      # ActiveRecord::AttributeMethods::Read#read_attribute. The default
+      # implementation just calls Value#cast.
+      #
+      # +value+ The raw input, as provided from the database.
+      def deserialize(value)
+        cast(value)
+      end
+
+      # Type casts a value from user input (e.g. from a setter). This value may
+      # be a string from the form builder, or a ruby object passed to a setter.
+      # There is currently no way to differentiate between which source it came
+      # from.
+      #
+      # The return value of this method will be returned from
+      # ActiveRecord::AttributeMethods::Read#read_attribute. See also:
+      # Value#cast_value.
+      #
+      # +value+ The raw input, as provided to the attribute setter.
+      def cast(value)
+        cast_value(value) unless value.nil?
+      end
+
+      # Casts a value from the ruby type to a type that the database knows how
+      # to understand. The returned value from this method should be a
+      # +String+, +Numeric+, +Date+, +Time+, +Symbol+, +true+, +false+, or
+      # +nil+.
+      def serialize(value)
+        value
+      end
+
+      # Type casts a value for schema dumping. This method is private, as we are
+      # hoping to remove it entirely.
+      def type_cast_for_schema(value) # :nodoc:
+        value.inspect
+      end
+
+      # These predicates are not documented, as I need to look further into
+      # their use, and see if they can be removed entirely.
+      def binary? # :nodoc:
+        false
+      end
+
+      # Determines whether a value has changed for dirty checking. +old_value+
+      # and +new_value+ will always be type-cast. Types should not need to
+      # override this method.
+      def changed?(old_value, new_value, _new_value_before_type_cast)
+        old_value != new_value
+      end
+
+      # Determines whether the mutable value has been modified since it was
+      # read. Returns +false+ by default. If your type returns an object
+      # which could be mutated, you should override this method. You will need
+      # to either:
+      #
+      # - pass +new_value+ to Value#serialize and compare it to
+      #   +raw_old_value+
+      #
+      # or
+      #
+      # - pass +raw_old_value+ to Value#deserialize and compare it to
+      #   +new_value+
+      #
+      # +raw_old_value+ The original value, before being passed to
+      # +deserialize+.
+      #
+      # +new_value+ The current value, after type casting.
+      def changed_in_place?(raw_old_value, new_value)
+        false
+      end
+
+      def ==(other)
+        self.class == other.class &&
+          precision == other.precision &&
+          scale == other.scale &&
+          limit == other.limit
+      end
+
+      private
+
+      # Convenience method for types which do not need separate type casting
+      # behavior for user and database inputs. Called by Value#cast for
+      # values except +nil+.
+      def cast_value(value) # :doc:
+        value
+      end
+    end
+  end
+end