Deprecating composed_of in ActiveRecord

This feature adds a lot of complication to ActiveRecord for dubious
value. Let's talk about what it does currently:

class Customer < ActiveRecord::Base
  composed_of :balance, :class_name => "Money", :mapping => %w(balance
amount)
end

Instead, you can do something like this:

    def balance
      @balance ||= Money.new(value, currency)
    end

    def balance=(balance)
      self[:value] = balance.value
      self[:currency] = balance.currency
      @balance = balance
    end

Since that's fairly easy code to write, and doesn't need anything
extra from the framework, if you use composed_of today, you'll
have to add accessors/mutators like that.

This feature will be removed in Rails 4.

1 files changed, 3 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/aggregations.rb b/activerecord/lib/active_record/aggregations.rb
index c39284539c..e7ed2644ca 100644
--- a/activerecord/lib/active_record/aggregations.rb
+++ b/activerecord/lib/active_record/aggregations.rb
@@ -161,6 +161,8 @@ module ActiveRecord
     #
     #   Customer.where(:balance => Money.new(20, "USD")).all
     #
+    # Note: +composed_of+ has been deprecated, and will be removed (with no
+    # replacement) in Rails 4.
     module ClassMethods
       # Adds reader and writer methods for manipulating a value object:
       # <tt>composed_of :address</tt> adds <tt>address</tt> and <tt>address=(new_address)</tt> methods.
@@ -203,6 +205,7 @@ module ActiveRecord
       #               :converter => Proc.new { |ip| ip.is_a?(Integer) ? IPAddr.new(ip, Socket::AF_INET) : IPAddr.new(ip.to_s) }
       #
       def composed_of(part_id, options = {})
+        ActiveSupport::Deprecation.warn("composed_of is deprecated, and will be removed in Rails 4. There is no replacement.")
         options.assert_valid_keys(:class_name, :mapping, :allow_nil, :constructor, :converter)
 
         name        = part_id.id2name