02-beerdb.md

Day 2 - beerdb Gem - Serve a Guinness Irish Stout or a Bamberg Aecht Schlenkerla Rauchbier Märzen as JSON - Free Home Delivery

Written by {% avatar geraldb %} Gerald Bauer

A code monkey and enthusiastic collector (and publisher) of open football and beer data. Skills include Ruby, SQLite and CSV. Spec lead of CSV <3 JSON.

What's the beerdb gem?

The beerdb gem offers a ready-to-use database schema (in SQL) and models such as - surprise, surprise - Beer, Brewery, Brand and friends (using the ActiveRecord object-relational mapper machinery). Example:

Let's try the brewery model:

by = Brewery.find_by( key: 'guinness' )

by.title
#=> 'St. James's Gate Brewery / Guinness Brewery'

by.country.key
#=> 'ie'

by.country.title
#=> 'Ireland'

by.city.title
#=> 'Dublin'

by.beers.first
#=> 'Guinness', 4.2

...

Or let's try the beer model:

b = Beer.find_by( key: 'guinness' )

b.title
#=> 'Guinness'

b.abv    # that is, alcohol by volume (abv)
#=> 4.2

b.tags
#=> 'irish_dry_stout', 'dry_stout', 'stout'

b.brewery.title
#=> 'St. James's Gate Brewery / Guinness Brewery'
...

What's it good for? Good question. Let's build an HTTP JSON service that serves up a Guinness Irish Stout or a Bamberg Aecht Schlenkerla Rauchbier Märzen as JSON? Example - GET /beer/guinness:

{
  "key": "guinness",
  "title": "Guinness",
  "synonyms": "Guinness Draught",
  "abv": "4.2",
  "srm": null,
  "og": null,
  "tags": ["irish_dry_stout","dry_stout","stout"],
  "brewery":
  {
    "key": "guinness",
    "title": "St. James's Gate Brewery / Guinness Brewery"
  },
  "country":
  {
    "key": "ie",
    "title": "Irland"
  }
}

Let's use Sinatra - a micro webframework - that offers a mini language, that is, domain-specific language (DSL) that lets you define routes, that is, HTTP methods paired with an URL-machting pattern and much more. For example, you can code the GET /beer/guinness route in Sinatra as get '/beer/guinness'. To make it into a route for any beer lets replace the guinness beer key with a placeholder, thus, resulting in get '/beer/:key'. Let's try -service.rb:

class BeerService < Sinatra::Base

  include BeerDb::Models     # lets (re)use the Beer, Brewery, etc. models

  get '/beer/:key' do |key|
    beer = Beer.find_by!( key: key )

    content_type :json       # set response to JavaScript Object Notation (JSON) content type

    { key:      beer.key,
      title:    beer.title,
      synonyms: beer.synonyms,
      abv:      beer.abv,
      srm:      beer.srm,
      og:       beer.og  }.to_json
  end

end

That's it. Ready to serve. Let's boot-up the beer service with a web server (e.g. Thin) using a Rack handler. Example - boot.rb:

require 'sinatra/base'    # note: sinatra will pull in web server machinery (e.g. rack, thin, etc.)
require 'beerdb/models'   # note: beerdb will pull in database access machinery (e.g. activerecord, etc.)

# database setup 'n' config
ActiveRecord::Base.establish_connection( adapter:  'sqlite3',
                                         database: './beer.db' )


require './service'

Rack::Handler::Thin.run BeerService.new, :Port => 9292

Try:

$ ruby ./boot.rb

Resulting in:

Thin web server (v1.6.3 codename Protein Powder)
Maximum connections set to 1024
Listening on 0.0.0.0:9292, CTRL+C to stop

Open up your browser and try http://localhost:9292/beer/guinness. Voila. Enjoy the Guinness responsibly. Cheers, Prost, Kampai, Na zdravi, Salute, 乾杯, Skål, Egészségedre!

Bonus: Let's add brewery details and more

Let's add brewery details to the beer service and lets add a new GET /brewery route. Example:

get '/beer/:key' do |key|
  beer = Beer.find_by!( key: key )

  brewery = {}
  if beer.brewery.present?
     brewery = { key:   beer.brewery.key,
                 title: beer.brewery.title }
  end

  tags = []
  if beer.tags.present?
     beer.tags.each { |tag| tags << tag.key }
  end

  country = {
    key:   beer.country.key,
    title: beer.country.title
  }

  content_type :json

  { key:      beer.key,
    title:    beer.title,
    synonyms: beer.synonyms,
    abv:      beer.abv,
    srm:      beer.srm,
    og:       beer.og,
    tags:     tags,
    brewery: brewery,
    country: country }.to_json
end


get '/brewery/:key' do |key|

  brewery = Brewery.find_by!( key: key )

  beers = []
  brewery.beers.each do |b|
    beers << { key: b.key, title: b.title }
  end

  tags = []
  if brewery.tags.present?
     brewery.tags.each { |tag| tags << tag.key }
  end

  country = {
    key:   brewery.country.key,
    title: brewery.country.title
  }

  content_type :json

  { key:      brewery.key,
    title:    brewery.title,
    synonyms: brewery.synonyms,
    since:    brewery.since,
    address:  brewery.address,
    web:      brewery.web,
    tags:     tags,
    beers:    beers,
    country:  country}.to_json
end

Bonus II: Let's use the json helper from sinatra contrib

If you think the code looks to enterprisey (that is, too complex):

get '/beer/:key' do |key|
  beer = Beer.find_by!( key: key )

  content_type :json       # set response to JavaScript Object Notation (JSON) content type

  { key:      beer.key,
    title:    beer.title,
    synonyms: beer.synonyms,
    abv:      beer.abv,
    srm:      beer.srm,
    og:       beer.og  }.to_json
end

Let's make it simpler using the json helper from the sinatra contrib package. In your boot script (e.g. boot.rb) add:

require 'sinatra/json'

And than you can use:

get '/beer/:key' do |key|
  beer = Beer.find_by!( key: key )

  json key:      beer.key,
       title:    beer.title,
       synonyms: beer.synonyms,
       abv:      beer.abv,
       srm:      beer.srm,
       og:       beer.og
end

The json helper will automatically set the json content type and call the #to_json method on the passed in data hash. More magic. Less configuration (code).

Find Out More

References

• Home :: github.com/beerkit/beer.db
• Gem :: beerdb
• Docs :: beerdb
• Datasets :: github.com/openbeer