Simple Rails Multi-Tenancy II

I suppose it's about time I updated my Simple Rails Multi-Tenancy post to use the latest rails 3.1.1. Not much has changed from the 3.0 beta to 3.1.1 in terms of the method I use to achieve multi-tenancy but the code has become a bit cleaner (but the patch required is a bit larger). This time around I'll skip the commands and just go straight to the code itself.

app/models/tenant.rb

class Tenant < ActiveRecord::Base
  class << self
    def current
      Thread.current[:tenant]
    end

    def current=(tenant)
      Thread.current[:tenant] = tenant
    end
  end

  validates :name, :host, presence: true

  def with
    previous, Tenant.current = Tenant.current, self
    yield
  ensure
    Tenant.current = previous
  end
end

app/models/tenant_scoped_model.rb

class TenantScopedModel < ActiveRecord::Base
  class << self
    def build_default_scope
      if method(:default_scope).owner != ActiveRecord::Base.singleton_class
        evaluate_default_scope { default_scope }
      elsif default_scopes.any?
        evaluate_default_scope do
          default_scopes.inject(relation) do |default_scope, scope|
            if scope.is_a?(Hash)
              default_scope.apply_finder_options(scope)
            elsif !scope.is_a?(ActiveRecord::Relation) && scope.respond_to?(:call)
              if scope.respond_to?(:arity) && scope.arity == 1
                scope = scope.call(self)
              else
                scope = scope.call
              end
              default_scope.merge(scope)
            else
              default_scope.merge(scope)
            end
          end
        end
      end
    end
  end

  self.abstract_class = true

  belongs_to :tenant

  default_scope do |model|
    model.where(:tenant_id => Tenant.current)
  end
end

app/controllers/application_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery

  around_filter :with_tenant

  protected
    attr_reader :current_tenant

    def with_tenant
      @current_tenant = Tenant.find_by_host!(request.host)
      @current_tenant.with { yield }
    end
end

app/helpers/application_helper.rb

module ApplicationHelper
  attr_reader :current_tenant
end

All of the migrations and the products model remain the same.

Demo sites are still set up: 3 that exist in the tenant table and 1 that does not. All code is available in a github repository.