ruby on rails - Rails5 - Adding Foreign Keys to Existing Models in postgres -

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i have 2 models. events model , eventoption. events have_many :event_options.

my issue when try migration add_foreign key :event_options, :events can link them up, following error:

activerecord::statementinvalid: pg::undefinedcolumn: error:  column "event_id" referenced in foreign key constraint not exist : alter table "event_options" add constraint "fk_rails_3995702fad" foreign key ("event_id")   references "events" ("id")

here's schema.rb:

activerecord::schema.define(version: 20160806001743)    # these extensions must enabled in order support database   enable_extension "plpgsql"    create_table "event_options", force: :cascade |t|     t.datetime "created_at",  null: false     t.datetime "updated_at",  null: false     t.float    "price"     t.text     "description"     t.string   "name"   end    create_table "events", force: :cascade |t|     t.datetime "created_at",                null: false     t.datetime "updated_at",                null: false     t.string   "name"     t.boolean  "active",     default: true   end    create_table "users", force: :cascade |t|     t.datetime "created_at",                     null: false     t.datetime "updated_at",                     null: false     t.string   "email",                          null: false     t.string   "encrypted_password", limit: 128, null: false     t.string   "confirmation_token", limit: 128     t.string   "remember_token",     limit: 128, null: false     t.index ["email"], name: "index_users_on_email", using: :btree     t.index ["remember_token"], name: "index_users_on_remember_token", using: :btree   end  end

i know there :id columns work because can play them in console. know i'm missing here foreign keys working app, life of me, don't know what.

wait, mean foreign key option has_many, isn't add_foreign_key confusingly. adds foreign key constraint.

so in migration need add_column or add_reference first

add_reference :event_options, :event, index: true  add_foreign_key :event_options, :events

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