ActiveRecord Problems using callbacks and STI - ruby-on-rails

Question

Hey folks, following problem with Rails and STI:
I have following classes:
class Account < AC::Base
has_many :users
end
class User < AC::Base
extend STI
belongs_to :account
class Standard < User
before_save :some_callback
end
class Other < User
end
end
module STI
def new(*args, &block)
type = args.dup.extract_options!.with_indifferent_access.delete(:type)
if type.blank? or (type = type.constantize) == self
super(*args, &block)
else
type.new(*args, &block)
end
end
end
And now the problem:
Without rewriting User.new (in module STI), the callback inside User::Standard gets never called, otherwise the account_id is always nil if I create users this way:
account.users.create([{ :type => 'User::Standard', :firstname => ... }, { :type => 'User::Other', :firstname => ... }])
If I'm using a different approach for the module like:
module STI
def new(*args, &block)
type = args.dup.extract_options!.with_indifferent_access.delete(:type)
if type.blank? or (type = type.constantize) == self
super(*args, &block)
else
super(*args, &block).becomes(type)
end
end
end
Then instance variables are not shared, because it's creating a new object.
Is there any solution for this problem without moving the callbacks to the parent class and checking the type of class?
Greetz
Mario

Answer 1

Maybe there's something I don't know, but I've never seen Rails STI classes defined in that manner. Normally it looks like...
app/models/user.rb:
class User < AC::Base
belongs_to :account
end
app/models/users/standard.rb:
module Users
class Standard < User
before_save :some_callback
end
end
app/models/users/other.rb:
module Users
class Other < User
end
end
It looks as though you are conflating class scope (where a class "lives" in relation to other classes, modules, methods, etc.) with class inheritance (denoted by "class Standard < User"). Rails STI relationships involve inheritance but do not care about scope. Perhaps you are trying to accomplish something very specific by nesting inherited classes and I am just missing it. But if not, it's possible it's causing some of your issues.
Now moving on to the callbacks specifically. The callback in Standard isn't getting called because the "account.users" relationship is using the User class, not the Standard class (but I think you already know that). There are several ways to deal with this (I will be using my class structure in the examples):
One:
class Account
has_many :users, :class_name => Users::Standard.name
end
This will force all account.users to use the Standard class. If you need the possibility of Other users, then...
Two:
class Account
has_many :users # Use this to look up any user
has_many :standard_users, :class_name => Users::Standard.name # Use this to look up/create only Standards
has_many :other_users, :class_name => Users::Other.name # Use this to look up/create only Others
end
Three:
Just call Users::Standard.create() and Users::Other.create() manually in your code.
I'm sure there are lots of other ways to accomplish this, but there are probably the simplest.

Answer 2

So I solved my problems after moving my instance variables to #attributes and using my second approach for the module STI:
module STI
def new(*args, &block)
type = args.dup.extract_options!.with_indifferent_access.delete(:type)
if type.blank? or (type = type.constantize) == self
super(*args, &block)
else
super(*args, &block).becomes(type)
end
end
end
class User < AR:Base
extend STI
belongs_to :account
validates :password, :presence => true, :length => 8..40
validates :password_digest, :presence => true
def password=(password)
#attributes['password'] = password
self.password_digest = BCrypt::Password.create(password)
end
def password
#attributes['password']
end
class Standard < User
after_save :some_callback
end
end
Now my instance variable (the password) is copied to the new User::Standard object and callbacks and validations are working. Nice! But it's a workaround, not really a fix. ;)