Rails STI：强制超类将关联委托给子类

Question

Here's the STI setup I've got so far:

class PhoneCall < ActiveRecord::Base
  belongs_to :from_phone_number, class_name: "PhoneNumber"
  belongs_to :to_phone_number, class_name: "PhoneNumber"
end

class OutgoingPhoneCall < PhoneCall
  has_one :user, through: :from_phone_number
end

class IncomingPhoneCall < PhoneCall
  has_one :user, through: :to_phone_number
end

You'll see that I expect a User at the end of either a from or to depending on its direction.

This works fine in some cases:

OutgoingPhoneCall.joins(:user).where(user: { id: 2 })

...gets me exactly what I want.

However, I cannot make the same call on the superclass

PhoneCall.joins(:user).where(user: {id: 2}).count
ActiveRecord::ConfigurationError: Association named 'user' was not found on PhoneCall; perhaps you misspelled it?
from /Users/xxxx/.rbenv/versions/2.2.0/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/associations/join_dependency.rb:218:in `find_reflection'

I would like a clean way to get a User 's phone calls without having to query twice.

How can I nudge my superclass PhoneCall to delegate this association to its subclasses?

Or, alternately, is there a way to get .joins to use the subclasses when querying?

Answer 1

您可以这样编写查询：

PhoneCall.joins(from_phone_number: :user, to_phone_number: :user).where(users: {id: 2})