How can I count and filter on an associated record in Rails?

Question

Company has_many Contacts

Company has_many ContactEmails :through => :contacts

ContactEmail belongs_to Contact

Contact belongs_to Company

Contact has_many ContactEmails

For a specific instance of Company, how can I find all ContactEmails and filter on an attribute, such as date_sent?

I tried Company.ContactEmails but I don't think it can make that association.

Answer 1

You probably want to use a named scope for this. This works for Rails 2.3, but wouldn't change much for Rails 3.

I haven't tested it, but something like this should work. The conditions may need to be tweaked for a proper date comparison.

ContactEmail < ActiveRecord::Base
  named_scope :by_date_sent, lambda {|d| { :conditions => ["date_sent = ?", d]}}
end

@company.contact_emails.by_date_sent(Date.today)

Answer 2

At least 2 semantic of ways to do it:

1. Through named_scope as Beerlington has suggested (The right way to do it).
2. Just pass the conditions to the finders:
   company.contact_emails.all(:conditions => ["date_sent = ?", d])