ActiveRecord dependent: :destroy requires id on the associated object, raises NoMethodError: undefined method `to_sym' for nil:NilClass

[spencerroan]

Steps to reproduce

# frozen_string_literal: true

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update
     your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "rails", github: "rails/rails"
  gem "arel", github: "rails/arel"
  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(
  adapter: "sqlite3",
  database: ":memory:"
)
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table(:doctors) {}

  create_table :appointments, id: false do |t|
    t.integer :doctor_id, null: false
  end
  create_table :tools, id: false do |t|
    t.integer :doctor_id, null: false
  end
end

class Doctor < ActiveRecord::Base
  has_many :appointments, dependent: :destroy
  has_many :tools, dependent: :delete_all
end

class Appointment < ActiveRecord::Base
end

class Tool < ActiveRecord::Base
end

class BugTest < Minitest::Test
  # dependent: destroy requires the association to have :id
  def test_destroy
    d = Doctor.create
    d.appointments << Appointment.new()
    assert d.destroy
  end

  # workaround 1: use delete_all and skip yer callbacks
  def test_delete_all
    d = Doctor.create
    d.tools << Tool.new()
    assert d.destroy
  end
  # workaround 2: give the association an id.
end

Expected behavior

The resource should be destroyed without raising an error.

Actual behavior

NoMethodError: undefined method `to_sym' for nil:NilClass

System configuration

Rails version:
ruby 2.4.2p198 (2017-09-14 revision 59899) [x86_64-linux]
Ruby version:
Rails 5.0.6

[sergiivorobei]

Seems this is a duplicate of #25437 issue.
Please view the comments.

Briefly: when you use dependent: :destroy each dependent model is going to be instantiated, and rails can't operate on them if they do not have the primary key, that is why it fails. In case of dependent: :delete_all rails are not going to initialize any dependent models so everything works fine.
It is expected behavior for associations. You should either add primary key (id or another field) or use dependent: :delete_all.

[al2o3cr]

+1 to @kennyx46 - dependent: :destroy is going to try to remove records by loading them and then calling destroy on each one.

That process - like most ActiveRecord processes - expects models to have a primary key (either id or something else, set by doing self.primary_key = ... in the model). I suspect you'd get the exact same to_sym error with code like this:

  tool = Tool.create
  tool.destroy

[kamipo]

It is expected behavior. See #25347 (comment)

[spencerroan]

Thank you for the update.

[bonafernando]

I had the same issue. Used to have a table like this:

CREATE TABLE user_country (
  id_user INTEGER(12) NOT NULL,
  id_country VARCHAR(15) NOT NULL,
  PRIMARY KEY (id_user,id_country),
  FOREIGN KEY (id_user) REFERENCES user(id),
  FOREIGN KEY (id_country) REFERENCES country(id)
);

With it, Active Record was always sending me warnings:

WARNING: Active Record does not support composite primary key.

And fixed creating a primary key for it:

CREATE TABLE user_country (
  id INTEGER(12) NOT NULL AUTO_INCREMENT,
  id_user INTEGER(12) NOT NULL,
  id_country VARCHAR(15) NOT NULL,
  PRIMARY KEY (id),
  FOREIGN KEY (id_user) REFERENCES user(id),
  FOREIGN KEY (id_country) REFERENCES country(id)
);

Not my favorite solution, but fixed...