Jack

Issue solved.
create_table :ways, id: false do |t|
ways must have id
create_table :ways do |t|

I have a model Station

class Station < ApplicationRecord
  validates :name, presence: true
  has_many :ways
  has_many :routes, through: :ways
  has_and_belongs_to_many :tickets

  def update_index_number(route, index_number)
    way = way(route)
        way.update(index_number: index_number) if way
  end

  def index_number_in(route)
    way(route).try(:index_number)
  end

  protected
  def way(route)
    @way ||= ways.where(route: route).first
  end
end

, Route model

class Route < ApplicationRecord
  validates :name, presence: true
  has_many :trains
  has_many :ways
  has_many :stations, through: :ways
end

and Way

class Way < ApplicationRecord
  belongs_to :station
  belongs_to :route
end

All migrations:

class CreateStations < ActiveRecord::Migration[5.2]
  def change
    create_table :stations do |t|
      t.string :name
    end
  end
end

class CreateRoutes < ActiveRecord::Migration[5.2]
  def change
    create_table :routes do |t|
      t.string :name
    end
  end
end

class WayJoinTable < ActiveRecord::Migration[5.2]
  def change
    create_table :ways, id: false do |t|
      t.belongs_to :station, index: true
      t.belongs_to :route, index: true
      t.integer :index_number, default: 10, null: false
    end
  end
end

But I can NOT write the :index_number!!

I also have this in routes:

  resources :stations do
    patch :update_index_number, on: :member
  end

This in station_controller:

  def update_index_number
    @station = Station.find(params[:id])
    @route = Route.find(params[:route_id])
    @station.update_index_number(@route, params[:index_number])
    redirect_to @route
  end

I get error:

ActiveRecord::StatementInvalid in StationsController#update_index_number
SQLite3::SQLException: no such column: ways.: UPDATE "ways" SET "index_number" = ? WHERE "ways"."" IS NULL
Extracted source (around line #12):
10 def update_index_number(route, index_number)
11     way = way(route)
12     way.update(index_number: index_number) if way
13 end

Please help somebody!
I belive in Rails and Community!