Setting default_address in Rails User model

I'm currently working on a model for a User that has_many :addresses; These addresses form a small address book from which a user can choose shipping and mailing addresses.

My question is, what's the the best way for me to tag one of the Address objects in the has_many relationship as the default address?

One way (I think I've got this right) would be to maintain this relationship:

class User < ActiveRecord::Base
  has_many :addresses, :dependent => :destroy
  has_one :default_address, :class_name => "Address"

class Address < ActiveRecord::Base
  belongs_to :user
  belo开发者_StackOverflowngs_to :user, :foreign_key :default_address_id

but I know that's sloppy, as I'll have two links between my default address and my user.

Should I be setting a default boolean in address, and grabbing the default using scope? (This adds an extra validation, as I don't want multiple default addresses... hmm.)

I figure this must come up fairly often in applications with address management, so figured I'd lay out my ideas and just ask. Any recommendations on best practices would be much appreciated.

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I'd add a 'is_default' flag to Addresses. Then you'll need a validation in the Addresses that is something like:

validates_uniqueness_of :is_default, :scope => :user_id, :unless => Proc.new { |address| address.is_default == 0 }

This will ensure you only get one default address but will allow for as many non-default addresses as you want.

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If it was me, I'd say the foreign key belongs on the User, with a boolean method on the address to figure out if its the default address (assuming you'll need that in your app):

class User < ActiveRecord::Base
  has_many :addresses, :dependent => :destroy
  belongs_to :default_address, :class_name => "Address"
end

class Address < ActiveRecord::Base
  belongs_to :user
  def default_address?
    user.default_address == self
  end
end

Another potential avenue is to give the address a boolean flag to indicate that its a default address and use an accessor in the User model to get to it:

class User
  has_many :addresses
  def default_address
    addresses.select(&:default_address?) #overly simple implementation
  end
end

Your app will need to handle the logic to ensure there's only one default address using the second arrangement.