Exception when destroying an object with :through association

rubyonrails-talk
1

I have an association such that a Person has many Events :through Attendees. When I attempt to destroy a Person object, I get the following exception:

ActiveRecord::StatementInvalid in PeopleController#destroy Mysql::Error: #42S22Unknown column 'id' in 'where clause': DELETE FROM attendees             WHERE `id` = NULL

There is no column `id` by design so it's not surprising that I get the error. Why is Rails looking for an id?

SCHEMA:

ActiveRecord::Schema.define(:version => 3) do

  create_table "attendees", :id => false, :force => true do |t|     t.column "event_id", :integer     t.column "person_id", :integer     t.column "bit_flags", :integer   end

  add_index "attendees", ["event_id"], :name => "index_attendees_on_event_id"   add_index "attendees", ["person_id"], :name => "index_attendees_on_person_id"

  create_table "events", :force => true do |t|     t.column "name", :string     t.column "description", :text     t.column "event_date", :date     t.column "start_time", :time     t.column "end_time", :time     t.column "last_register_date", :date     t.column "location_city", :string     t.column "location_state", :string, :limit => 2     t.column "location_zip", :string, :limit => 9     t.column "location_addr", :text     t.column "agenda", :text     t.column "contacts", :text   end

  create_table "people", :force => true do |t|     t.column "first_name", :string     t.column "last_name", :string     t.column "title", :string     t.column "organization", :string     t.column "email", :string     t.column "phone1", :string     t.column "phone2", :string   end

end

MODELS:

class Person < ActiveRecord::Base   has_many :attendees, :dependent => :destroy   has_many :events, :through => :attendees, :uniq => true end

class Event < ActiveRecord::Base   has_many :attendees, :dependent => :destroy   has_many :people, :through => :attendees, :uniq => true end

class Attendee < ActiveRecord::Base belongs_to :event belongs_to :person end

Any ideas? Thanks, Stan

2

I have an association such that a Person has many Events :through Attendees. When I attempt to destroy a Person object, I get the following exception:

ActiveRecord::StatementInvalid in PeopleController#destroy Mysql::Error: #42S22Unknown column 'id' in 'where clause': DELETE FROM attendees            WHERE `id` = NULL

There is no column `id` by design so it's not surprising that I get the error. Why is Rails looking for an id?

Because rails expects every table to have a primary key (the exception
was the old habtm join tables). With has_many :through, the join model
is a model in its own right so rails expects it to have a primary key.

Fred

3

With has_many :through, the join model is a model in its own right so rails expects it to have a primary key.

Ah. Thanks.