Rails: Scaffold to automatically do one-to-many relationship

Question

Not sure if I\'m reading this right, but it seems like Scaffold will not do a one-to-many relationship in its entirety. For instance, if I create messages with

Answer 1

You don't need a heavy rails admin framework to get one-to-many relationships working.

You can use scaffolding to get most of the way there.

A little more work in the controller and _form view will get you the rest of the way there.

Here's how...

Story: Select a beer for a developer

In order to select a beer for a developer
As an admin
I want a mainly scaffolded interface to select that beer

Scenario 1: Select beer for new developer
Given I have clicked the  button  and entered the developer's name
When I click the beer dropdown
Then I should be presented with a list of beers to choose from
And that beer will be saved when I click 

Scenario 2: Select a different beer for existing developer
Given I have clicked the  button on the index page for a particular developer
When I click the beer dropdown
Then I should be presented with a list of beers to choose from
And that beer will be saved when I click 

Assuming we have a beers table:

  create_table "beers", force: true do |t|
    t.string   "name"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

And a developers table that has a foreign key (beer_id) referencing the beers table:

  create_table "developers", force: true do |t|
    t.string   "name"
    t.integer  "beer_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

We can use scaffolding to create both tables:

$ rails g scaffold beer name

$ rails g scaffold developer name beer_id:integer

The scaffold command creates the controllers and views for each model.

We will need to modify our controllers and views a little bit to get the dropdown menu to select a beer for each developer:

app/views/developers/_form.html.erb

Replace the generated text_field and label for beer_id with the following:

  

    <%= f.label :beer_id %>

    <%= collection_select(:developer, :beer_id, @beers, :id, :name, {:prompt => false}) %> 
  

app/controllers/developer_controller.rb

Edit the controller's new and edit methods:

  # GET /developers/new
  def new
    @developer = Developer.new
    @beers = Beer.all
    respond_to do |format|
      format.html # new.html.erb
    end
  end


  # GET /developers/1/edit
  def edit
    @beers = Beer.all
    respond_to do |format|
      format.html # new.html.erb
    end    
  end

Screen Shots

Notes

Rails scaffolding is great. Look at all the files that it creates for you:

$ be rails g scaffold beer name
      invoke  active_record
      create    db/migrate/20140912144218_create_beers.rb
      create    app/models/beer.rb
      invoke    rspec
      create      spec/models/beer_spec.rb
      invoke      factory_girl
      create        spec/factories/beers.rb
      invoke  resource_route
       route    resources :beers
      invoke  scaffold_controller
      create    app/controllers/beers_controller.rb
      invoke    erb
      create      app/views/beers
      create      app/views/beers/index.html.erb
      create      app/views/beers/edit.html.erb
      create      app/views/beers/show.html.erb
      create      app/views/beers/new.html.erb
      create      app/views/beers/_form.html.erb
      invoke    rspec
      create      spec/controllers/beers_controller_spec.rb
      create      spec/views/beers/edit.html.erb_spec.rb
      create      spec/views/beers/index.html.erb_spec.rb
      create      spec/views/beers/new.html.erb_spec.rb
      create      spec/views/beers/show.html.erb_spec.rb
      create      spec/routing/beers_routing_spec.rb
      invoke      rspec
      create        spec/requests/beers_spec.rb
      invoke    helper
      create      app/helpers/beers_helper.rb
      invoke      rspec
      create        spec/helpers/beers_helper_spec.rb
      invoke    jbuilder
      create      app/views/beers/index.json.jbuilder
      create      app/views/beers/show.json.jbuilder
      invoke  assets
      invoke    coffee
      create      app/assets/javascripts/beers.js.coffee
      invoke    scss
      create      app/assets/stylesheets/beers.css.scss
      invoke  scss
      create    app/assets/stylesheets/scaffolds.css.scss

All you have to do is know which files to modify when you want more than basic CRUD operations.

Hope that helps. ~ Lex