Currently we have a list of narrations the user can click on to go to the narration’s show page. From there, they can navigate back to the narrations list or view the original article in a new tab. Looking forward, I’d like to not only show who narrated the narration, but let the listener click on their name/avatar, and then go to their profile page. Each narrator will have many narrations. Each narration will have exactly one narrator. We could have duos some day, but we’ll table that until we need it. So let’s get started; beginning with the end in mind, I’d like to start from the Narration view. Let’s add a link to take us to a Narrator show page:

= @narration.title
= link_to 'Narrated by Narrator', narrator_path

There’s some pseudo-code as a placeholder for now. I can envision the Narrator table having a first_name and last_name column, and I’ll need to use the Narrator controller to create a #full_name method. But first, let’s define the route narrator_path:

get 'narrator/:id', to: 'narrators#show', as: :narrator

Here’s the error we get if we click on the link in this state:

Routing Error
uninitialized constant NarratorsController

So in case you were wondering whether we should create our model or controller next, now you know! Let’s make a new file called app/controllers/narrators_controller.rb and give it a show method:

class NarratorsController < ApplicationController
  def show
  end
end

Here’s my next error in the browser:

ActionController::UnknownFormat in NarratorsController#show
NarratorsController#show is missing a template for this request format and variant.

Now let’s create app/views/narrators/show.html.haml:

%h4 Welcome to the Narrator show page.

Now each Narration show page has a link that takes us to its Narrator show page, sort of. Our route is using the same id as the Narration. Let’s create our Narrator model now and add some data to shine some light, app/models/narrator.rb:

class Narrator < ApplicationRecord
end

Now, let’s create a migration, db/migrate/20170728110334_create_narrators.rb, and similar to Twitter, to give personality and possible anonymity, let’s give the Narrator a username:

class CreateNarrators < ActiveRecord::Migration[5.1]
  def change
    create_table :narrators do |t|
      t.string :first_name
      t.string :last_name
      t.string :username
      t.timestamps
    end
  end
end

Run rails db:migrate:

== 20170728110330 CreateNarrators: migrating ==================================
-- create_table(:narrators)
   -> 0.0961s
== 20170728110330 CreateNarrators: migrated (0.0964s) =========================

Now let’s create some seed data to work with. Here’s what I’ll drop into seeds.rb and then run rails db:seed:

narrators_array = [
  {first_name: 'Aaron', last_name: 'Kelton', username: 'chemturion'},
  {first_name: 'Morgan', last_name: 'Freeman', username: 'shawshank'}
]
narrators_array.each do |rec|
  Narrator.find_or_create_by(first_name: rec[:first_name], last_name: rec[:last_name], username: rec[:username])
end

I double checked that duplicate records weren’t created for Narrations and confirmed using rails db and select * from narrators; that we have our table populated:

id | first_name | last_name |  username  
----+------------+-----------+-----------
 1 | Aaron      | Kelton    | chemturion
 2 | Morgan     | Freeman   | freeman

Now for the purpose of demonstration, how can we assign a narrator to a narration? Let’s suppose I narrated the “Life in Short” article, and Morgan Freeman narrated the “Drugs and the Meaning of Life” article. Generically, I the Narrator could have many narrations. Let’s define this relationship in each model file. First, app/models/narrator.rb has_many narrations:

class Narrator < ApplicationRecord
  has_many :narrations
end

And second, app/models/narration.rb belongs_to a narrator:

class Narration < ApplicationRecord
  belongs_to :narrator
end

Now, conceptually this makes me think that only the Rails objects know about each other. I’m not sure that we’ve successfully linked the data in the tables together using a foreign key. Since we’ve already generated a migration to create the tables, let’s generate a migration to add the connections. Here’s the Rails Guide that helped me: http://edgeguides.rubyonrails.org/association_basics.html#updating-the-schema. Unfortunately their migration isn’t for after the table’s been created. Let’s do something comparable, so new file db/migrate/20170728114023_add_reference_to_narrations.rb and using http://api.rubyonrails.org/v5.1.2/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_reference as guidance:

class AddReferenceToNarrations < ActiveRecord::Migration[5.1]
  def change
    add_reference :narrations, :narrator, foreign_key: true
  end
end

Running rails db:migrate gives us:

== 20170728114023 AddReferenceToNarrations: migrating =========================
-- add_reference(:narrations, :narrator, {:foreign_key=>true})
   -> 0.1256s
== 20170728114023 AddReferenceToNarrations: migrated (0.1258s) ================

Now let’s look inside running rails db and select * from narrations;. We should see a narrator_id column, but we can also confirm by looking in our db/schema.rb file:

ActiveRecord::Schema.define(version: 20170728114023) do

  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"

  create_table "narrations", force: :cascade do |t|
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "title"
    t.boolean "published"
    t.string "source_url"
    t.bigint "narrator_id"
    t.index ["narrator_id"], name: "index_narrations_on_narrator_id"
  end

  create_table "narrators", force: :cascade do |t|
    t.string "first_name"
    t.string "last_name"
    t.string "username"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  add_foreign_key "narrations", "narrators"
end

Notice that the narrations table has a column named narrator_id with type bigint, and an index on that column. Nothing changed for the narrator table, but at the end of the schema.rb file, we have the add_foreign_key statement. Ok, back to the use case.

When a narrator creates a narration, their id will be plopped into the narration table as narrator_id. But for now using sample data, I think I’ll need to manually put that into my seeds.rb file and do the whole reset & load dance rails db:reset.

narrations_array = [
  {title: 'Life Is Short',                  published: true,  source_url: 'http://www.paulgraham.com/vb.html', narrator_id: 1},
  {title: 'Drugs and the Meaning of Life',  published: true,  source_url: 'https://www.samharris.org/podcast/item/drugs-and-the-meaning-of-life', narrator_id: 2},
  {title: 'The Power Of A Digital Sabbath', published: false, source_url: 'https://feld.com/archives/2017/02/power-digital-sabbath.html', narrator_id: 2}
]

narrations_array.each do |rec|
  Narration.find_or_create_by(title: rec[:title], published: rec[:published], source_url: rec[:source_url], narrator_id: rec[:narrator_id])
end

After the reset, here’s my feedback:

Dropped database 'narify_development'
Dropped database 'narify_test'
Created database 'narify_development'
Created database 'narify_test'
-- enable_extension("plpgsql")
   -> 0.0463s
-- create_table("narrations", {:force=>:cascade})
   -> 0.0403s
-- create_table("narrators", {:force=>:cascade})
   -> 0.0086s
-- add_foreign_key("narrations", "narrators")
   -> 0.0162s
-- enable_extension("plpgsql")
   -> 0.0468s
-- create_table("narrations", {:force=>:cascade})
   -> 0.0248s
-- create_table("narrators", {:force=>:cascade})
   -> 0.0130s
-- add_foreign_key("narrations", "narrators")
   -> 0.0755s

Now, let’s jump back into the narrators_controller.rb and assign the narrator in question to the @narrator instance variable.

class NarratorsController < ApplicationController
  def show
    @narrator = Narrator.find(params[:id])
  end
end

I’m not totally sure this is going to work. I think the params dude is going to pass an :id, but I’m not sure how it knows to pass the narration.narrator_id, if that makes sense. Let’s add this little code to our narrator’s show view:

%h4 Welcome to the Narrator show page.
= @narrator.username

Unfortunately, my narrator’s id matches the narration id, so I can’t fully tell if it’s working. To test, let’s change the published value for narration id=3 to true, and see if the corresponding narrator route tries to pull 3 instead of 2… And it’s pulling the wrong id. So I think we should now modify our link_to helper in app/views/narrations/show.html.haml:

= link_to 'Narrated by ' + @narration.narrator.username, narrator_path(@narration.narrator)

Now we can navigate to the narrator show page from the narration show page. Next thing we want to do is list all the narrations for the narrator when we go to their page, similar to seeing a user’s Tweets on their Twitter profile page.