Rails ActiveModel lookup with delegate

Question

I hope the question is worded correctly since I'm unsure of what I am actually trying to accomplish, but here goes...

I got some advice in a Rails book that my DB logic/lookups should actually be handled in my Models instead of Controllers... that makes sense. So, I'm trying to move over the functionality to my Models, but running into an issue right off the bat.

In this case, I'd like to find hosts with a security_percentage below 99%.

models/network_host.rb

class NetworkHost < ActiveRecord::Base
  acts_as_paranoid

  belongs_to :location
  has_many :network_host_tests, dependent: :destroy
  has_many :parent_tests, through: :network_host_tests
  has_many :deferred_hosts

  validates_presence_of :location, :mac_address, :ip_address
  validates_uniqueness_of :mac_address

  delegate :security_percentage, to: :last_test, allow_nil: true

  def last_test
    network_host_tests.last
  end

  def test_before_last_test
    network_host_tests.offset(1).last
  end

  def self.hosts_at_risk
    where.not(security_percentage: 99)
  end
end

However, when testing my 'new' code out in the rails console , I get this:

$ NetworkHost.hosts_at_risk 
PG::UndefinedColumn: ERROR:  column network_hosts.security_percentage does not exist LINE 1: ...  WHERE "network_hosts"."deleted_at" IS NULL AND ("network_h...
                                                             ^ : SELECT "network_hosts".* FROM "network_hosts"  WHERE
"network_hosts"."deleted_at" IS NULL AND ("network_hosts"."security_percentage" != 99)

I assume this is because of my delegate :security_percentage, to: ... line.

So, security_percentage is a virtual variable, found through the table network_host_tests .

Is this my issue? Is it fixable?

Answer 1

It looks like you just want to do a joins to the correct table

def self.hosts_at_risk
  joins(:network_host_tests).where.not(network_host_tests: { security_percentage: 99 })
end

Although this isn't just checking the last test anymore, it would be checking all of them. To narrow it down to the last test you'd have to do some more work, but it'd help to know what your original controller was doing to get it