rails3-amf - to_amf method not found on ActiveRecord objects

I am using the rails3-amf gem by warhammerkid in my Rails 3 / Flex 4 project.

AFAIK, I have correctly followed the "Getting Started" instructions from the GitHub page.

• I have added the gem lines to my Gemfile.
• I have installed the gems using bundle install.
• From my Flex application, I will be making the RemoteObject call to the index action in the ManageMySchool::GradesController file. This is the code in the app/controllers/manage_my_school/grades_controller.rb file:

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

• The name of the model which is to be serialized is called Grade in both the Rails project (app/models/Grade.rb) and the Flex project (Grade.as with a RemoteAlias set as Grade). In the config/application.rb file, I have done the class mapping this way:

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

• And I have done a parameter mapping this way:

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

Problem

Now, when I run the server and make the RemoteObject call from Flex, I get a to_amf undefined method error for the Grade model.

If I change Grade.first to Grade.all, @grade would have an array of Grades. But the undefined method error message still mentions the Grade model. This means that the to_amf method is working for the Array class but not for the ActiveRecord model.

Why is this? What am I doing wrong?

Is there something I have to do to "enable" the rails3-amf gem for ActiveRecord models?

I would appreciate any insights. Thanks!

Update

@warhammerkid: Here is the output of Grade.ancestors as seen in rails console.

ree-1.8.7-2011.03 :006 > puts Grade.ancestors
Grade
ActiveRecord::Base
Paperclip::CallbackCompatability::Rails3::Running
P开发者_运维问答aperclip::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

Note that only ActiveModel::Serialization is there. No mention of Rails3AMF.

Does this mean I have to do something special to load the Rails3AMF module for the ActiveRecord models?

I am using Rails 3.0.5 with the latest version of ree. The gems are all contained in a gemset managed using rvm.

Update 2

If I remove the to_amf in the render :amf line, then I get the following error:

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

Update 3

If I manually add the line include Rails3AMF::Serialization at the top of the Grade.rb model file, then it all works. So, does this mean that I have to put this line in all my models?

I see that this is already being done in line numbers 40 - 42 in the lib/rails3-amf/serialization.rb file of the gem:

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

Why isn't this working? Should I force-load the gem when my application initializes or something?

Thanks!

Update 4 - Solved by this workaround

Okay, I just ended up adding this code block in an initializer:

class ActiveRecord::Base
    include Rails3AMF::Serialization  
end

And it is working.

@warhammerkid - Thanks for the help.

Rails3AMF::Serialization, the module that adds the to_amf method, is included in ActiveModel::Serialization when Rails3-AMF loads. If it's somehow not being included even though the code is running and ActiveModel::Serialization is one of your model's ancestors, then the simplest solution is just to add "include Rails3AMF::Serialization" at the top of your model implementation. I've never tried gem sets before, but it might be an issue with them, as everything works correctly using Bundler.

As an aside, feel free to post a bug to https://github.com/warhammerkid/rails3-amf/issues.