CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-5database-migration
user2509710
user2509710

Reputation: 99

Rails migration for has_and_belongs_to_many

This is driving me BANANAS. I've tried the migration multiple ways, but the relationship only seems to go one way. I would like a relationship where I can Event.first.subjects << Subject.first and Event.last.subjects << Subject.first

class Event < ApplicationRecord
    has_and_belongs_to_many :subjects 
end

class Subject < ApplicationRecord
    has_and_belongs_to_many :events
end

I created a migration with

rails g migration CreateJoinTableEventSubject events subjects

class CreateJoinTableEventSubject < ActiveRecord::Migration[5.2]
  def change
    create_join_table :events, :subjects do |t|
      t.index [:event_id, :subject_id]
      t.index [:subject_id, :event_id]
    end
  end
end

I can Subject.first.events which I don't need but Event.first.subjects returns

ActiveRecord::StatementInvalid (SQLite3::SQLException: no such column: subjects.event_id: SELECT  "subjects".* FROM "subjects" WHERE "subjects"."event_id" = ? LIMIT ?)

Here is the schema.rb:

ActiveRecord::Schema.define(version: 2020_07_07_183602) do

  create_table "events", force: :cascade do |t|
    t.string "title"
    t.text "description"
    t.date "date"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  create_table "events_subjects", id: false, force: :cascade do |t|
    t.integer "event_id", null: false
    t.integer "subject_id", null: false
    t.index ["event_id", "subject_id"], name: "index_events_subjects_on_event_id_and_subject_id"
    t.index ["subject_id", "event_id"], name: "index_events_subjects_on_subject_id_and_event_id"
  end

  create_table "subjects", force: :cascade do |t|
    t.string "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

end

Upvotes: 0

Views: 278

Answers (1)

user2509710
user2509710

Reputation: 99

So I had been clearing the DB by just deleting the development.sqlite3 file. When I actually ran rails db:drop for this and ran the migrations it started working. I guess there's some artifact that was preserved without actually dropping the db?

Thanks to the commenters for making me think of this.

Upvotes: 1

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