Retactoring advanced has_many example - ruby-on-rails

Question

My user model has three relations for the same message model, and is using raw SQL :/ Is there a better more rails way to achieve the same result?
Could the foreign key be changed dynamically? e.g User.messages.sent (foreign key = author_id) and User.messages.received (foreign key = recipient ) I have been trying to move some of the logic into scopes in the message model, but the user.id is not available from the message model...
Any thoughts?
Table layout:
create_table "messages", :force => true do |t|
t.string "subject"
t.text "body"
t.datetime "created_at"
t.datetime "updated_at"
t.integer "author_id"
t.integer "recipient_id"
t.boolean "author_deleted", :default => false
t.boolean "recipient_deleted", :default => false
end
This is my relations for my user model:
has_many :messages_received, :foreign_key => "recipient_id", :class_name => "Message", :conditions => ['recipient_deleted = ?', false]
has_many :messages_sent, :foreign_key => "author_id", :class_name => "Message", :conditions => ['author_deleted = ?', false]
has_many :messages_deleted, :class_name => "Message", :finder_sql => 'SELECT * FROM Messages WHERE
author_id = #{self.id} AND author_deleted = true OR
recipient_id = #{self.id} AND recipient_deleted = true'
Best regards.
Asbjørn Morell

Answer 1

Yes, use a named_scope for sorting between deleted and not deleted messages.
class User < ActiveRecord::Base
has_many :messages_received, :foreign_key => 'recipient_id'
has_many :messages_sent, :foreign_key => 'author_id'
end
class Messages < ActiveRecord::Base
named_scope :deleted, :conditions => 'author_deleted = TRUE OR recipient_deleted = TRUE'
named_scope :not_deleted, :conditions => 'author_deleted = FALSE OR recipient_deleted = FALSE'
end
# Example user
user = User.first
user.messages_received.deleted
user.messages_received.not_deleted
user.messages_sent.deleted
user.messages_sent.not_deleted
Alternatively, you could go one step further and simplfy the association by using the user_id as the foreign key and specifying the message type.
create_table "messages", :force => true do |t|
t.string "subject"
t.text "body"
t.datetime "created_at"
t.datetime "updated_at"
t.string "message_type"
t.integer "user_id"
t.boolean "deleted", :default => false
end
class User < ActiveRecord::Base
has_many :messages
end
class Messages < ActiveRecord::Base
MESSAGE_TYPES = %w[Recipient Author]
belongs_to :user
named_scope :recipient, :conditions => {:message_type => 'Recipient'}
named_scope :author, :conditions => {:message_type => 'Author'}
named_scope :deleted, :conditions => {:deleted => true}
named_scope :not_deleted, :conditions => {:deleted => false}
# Convenience class methods
def self.sent
author.not_deleted
end
def self.received
recipient.not_deleted
end
end
# Example usage
user = User.first
user.messages.sent
user.messages.received
user.messages.deleted
This approach is advantagoues because:
One less column.
Extendable. Adding an additional message type in the future is trivial (Eg: Drafts).