Question

I’ve been banging my head on this one for a while. Someone please resque me.

Scenario

I have the following models

class House < ActiveRecord::Base
  has_one :tenancy, :dependent => :destroy, :as => :tenant
end

class LeaseAgreement < ActiveRecord::Base
  has_many :tenancies
end

class Tenancy < ActiveRecord::Base
  belongs_to :tenant, :polymorphic => true
  belongs_to :lease_agreement

  def lease=(lease)
    if lease.rent_amount > 10000
      # do something here
    else
      # do something else here
    end

    self.lease_agreement = lease
  end
end

My factories

Factory.define :lease_agreement do |l|
  l.name "Foo"
  l.rent_amount 5000
end

Factory.define :tenancy do |t|
  t.name "Foo"
  t.association :tenant, :factory => :house
  t.after_build { |tenancy| tenancy.lease = Factory.create(:lease_agreement) }
end

also tried this

Factory.define :tenancy do |t|
  t.name "Foo"
  t.association :tenant, :factory => :house
  t.after_build { |tenancy| tenancy.lease = Factory.create(:lease_agreement, :tenant => tenancy) }
end

Both ways in my spec tests when I try this; @house = Factory(:house) I get the following error

NoMethodError: undefined method `rent_amount' for nil:NilClass
from /home/kibet/.rvm/gems/ruby-1.8.7-p352/gems/activesupport-3.0.5/lib/active_support/whiny_nil.rb:48:in `method_missing'
from /home/kibet/code/ruby/stuff/app/models/tenancy.rb:44:in `lease='

How would I go about this?

Answer 1

It looks like an order of operations problem, I think lease is being set to nil before it evaluates your after_build hook where lease is a legit LeaseAgreement instance.

You code can’t handle a nil lease being passed in, which is a legitimate value if you want to clear the association. Try handling the nil like so:

class Tenancy < ActiveRecord::Base
  belongs_to :tenant, :polymorphic => true
  belongs_to :lease_agreement

  def lease=(lease)
    if lease.present? && lease.rent_amount > 10000
      # do something here
    else
      # do something else here
    end

    self.lease_agreement = lease
  end
end

The code as written will always produce an error with a nil lease passed in.