How do I address Arel incompatibility with Hartl Rails Tutorial (Ch. 2)?

Question

I'm currently working along with Hartl's Ruby on Rails tutorial (Ch. 2) using Cloud9's IDE. I'm running into an error with Arel::Nodes::BindParam.new that is being caused by yesterday's release of Arel 6.0.0. The issue is that BindParam no longer accepts parameters, and is being passed one by ActiveRecord. To address this problem earlier on while using rake db:migrate, I set a different version of Arel in my Gemfile as explained by aaron-k here. However, this change has not prevented me from getting the same error while trying to create a 'new user' from the scaffolded Users resource in the tutorial:

ArgumentError in UsersController#create
wrong number of arguments (1 for 0)

Extracted source (around line #271):
269   # NOTE: The column param is currently being used by the sqlserver-adapter
270   def substitute_at(column, index)
271     Arel::Nodes::BindParam.new '?'
272   end

  # REFERENTIAL INTEGRITY ====================================

Rails.root: /home/ubuntu/workspace/toy_app

app/controllers/users_controller.rb:30:in `block in create'
app/controllers/users_controller.rb:29:in `create'

I see no reference to Arel in users_controller.rb, and so I am wondering where else I need to require an older version of Arel. Could this be a problem with hosting it through Cloud9 using rails server?

Answer 1

An update to the Arel gem broke migrations in Rails 4 beta. See here for details. The tutorial has already been updated with the fix.