rails3-amf-在ActiveRecord对象上找不到to_amf方法

bundle install

ManageMySchool::GradesController

index

app/controllers/manage_my_school/grades_controller.rb

class ManageMySchool::GradesController < ApplicationController  
    respond_to :html, :amf  

    def index
        @grade = Grade.first
        respond_with(@grade) do |format|
            format.amf { render :amf => @grade.to_amf }
        end
    end 
end

app/models/Grade.rb

Grade.as

RemoteAlias

Grade

Grade

config/application.rb

config.rails3amf.class_mapping do |m|
    m.map :as => \'Grade\', :ruby => \'Grade\'  
end

config.rails3amf.map_params :controller => \'ManageMySchool::GradesController\', :action => \'index\', :params => [:authenticity_token]

Grade

to_amf undefined method

Grade.first

Grade.all

@grade

undefined method

to_amf

ree-1.8.7-2011.03 :006 > puts Grade.ancestors
Grade
ActiveRecord::Base
Paperclip::CallbackCompatability::Rails3::Running
Paperclip::CallbackCompatability::Rails3
Paperclip::Glue CanCan::ModelAdditions
Authlogic::ActsAsAuthentic::ValidationsScope
Authlogic::ActsAsAuthentic::SingleAccessToken
Authlogic::ActsAsAuthentic::SessionMaintenance
Authlogic::ActsAsAuthentic::RestfulAuthentication::InstanceMethods
Authlogic::ActsAsAuthentic::RestfulAuthentication
Authlogic::ActsAsAuthentic::PersistenceToken
Authlogic::ActsAsAuthentic::PerishableToken
Authlogic::ActsAsAuthentic::Password
Authlogic::ActsAsAuthentic::MagicColumns
Authlogic::ActsAsAuthentic::Login
Authlogic::ActsAsAuthentic::LoggedInStatus
Authlogic::ActsAsAuthentic::Email
Authlogic::ActsAsAuthentic::Base
ActiveRecord::Aggregations
ActiveRecord::Transactions
ActiveRecord::Reflection
ActiveRecord::Serialization
ActiveModel::Serializers::Xml
ActiveModel::Serializers::JSON
ActiveModel::Serialization
ActiveRecord::AutosaveAssociation
ActiveRecord::NestedAttributes
ActiveRecord::Associations
ActiveRecord::AssociationPreload
ActiveRecord::NamedScope
ActiveModel::Validations::Callbacks
ActiveRecord::Callbacks
ActiveModel::Observing
ActiveRecord::Timestamp
ActiveModel::MassAssignmentSecurity
ActiveRecord::AttributeMethods::Dirty
ActiveModel::Dirty
ActiveRecord::AttributeMethods::TimeZoneConversion
ActiveRecord::AttributeMethods::PrimaryKey
ActiveRecord::AttributeMethods::Read
ActiveRecord::AttributeMethods::Write
ActiveRecord::AttributeMethods::BeforeTypeCast
#<Module:0x1028356f0> ActiveRecord::AttributeMethods::Query
ActiveRecord::AttributeMethods
ActiveModel::AttributeMethods
ActiveRecord::Locking::Optimistic
ActiveRecord::Locking::Pessimistic
ActiveRecord::Validations
ActiveModel::Validations::HelperMethods
ActiveModel::Validations
ActiveSupport::Callbacks
ActiveModel::Conversion
ActiveRecord::Persistence Object
PP::ObjectMixin Base64::Deprecated
Base64
ActiveSupport::Dependencies::Loadable
Kernel

Rails3AMF

render :amf

to_amf

Grade Load (0.3ms)  SELECT `grades`.* FROM `grades` LIMIT 1
Completed 200 OK in 195ms (Views: 0.1ms | ActiveRecord: 0.8ms)
Sending back AMF

NoMethodError (You have a nil object when you didn\'t expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.last):


Rendered /Users/anjan/.rvm/gems/ree-1.8.7-2011.03@rb/gems/actionpack-3.0.5/lib/>     >     action_dispatch/middleware/templates/rescues/_trace.erb (1.1ms)
Rendered /Users/anjan/.rvm/gems/ree-1.8.7-2011.03@rb/gems/actionpack-3.0.5/lib/>     >     action_dispatch/middleware/templates/rescues/_request_and_response.erb (2.8ms)
Rendered /Users/anjan/.rvm/gems/ree-1.8.7-2011.03@rb/gems/actionpack-3.0.5/lib/>     >     action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (13.6ms)


Started POST \"/amf\" for 127.0.0.1 at Fri Apr 15 17:03:34 +0530 2011
Sending back AMF

Grade.rb

include Rails3AMF::Serialization

lib/rails3-amf/serialization.rb

# Hook into any object that includes ActiveModel::Serialization
module ActiveModel::Serialization
    include Rails3AMF::Serialization
end

class ActiveRecord::Base
    include Rails3AMF::Serialization  
end