RubyTapas #184 - #188

184 Sequel, Postgres, JSON

★

PG extension

require "sequel"
Sequel.extension(:pg_json)
Sequel.extension(:pg_json_ops)

...
DB[:dpd_subscriber_dump].import([:subscriber], data.map{|s| [Sequel.pg_json(s)]})

• DB = Sequel.connect
• row = DB[:dpd_subscriber_dump].detect
• DB.alter_table :dpd_subscriber_dump do
  • add_index Sequel.lit

185 Two Refactorings

★

functional programming style

  def enumerate_episodes(summaries, last_number)
    summaries.inject(last_number) do |last_number, ep_summary| # !> shadowing outer local variable - last_number
      episode = yield ep_summary, last_number + 1
      episode.number
    end
  end

でも理解しにくい

別の方法

  class EpisodeEnumeration
    def initialize
      @next_number = 1
    end

    def number_episode(episode)
      number = episode.number
      if number
        @next_number = number
      else
        episode.number = @next_number
      end
      @next_number += 1
    end
  end

...

episode_enumeration = EpisodeEnumeration.new
...
episode_enumeration.number_episode(episode)

Embrace state

3つ目

Third approach is to go to the source of the data, and make sure there are no episodes with the number missing from their titles in the first place!

186 Keyword Arguments

★

引数の必須チェック、エラーの出し方とか 引数を打ち間違えたときの動きとか

次のものはtypoが分からない

def order_burger(customer_name, options={})
  has_cheese = options.fetch(:cheese)

def order_burger(customer_name, options={})
  patty_type = options.delete(:patty)  { :beef }
...
  if options.any?
    raise ArgumentError, "Unrecognized option(s): #{options}"
  end

cheeseにデフォルト値が無い

def order_burger(customer_name, patty: :beef, cheese:, onions: true, bacon: false)

typo

def order_burger(customer_name, patty: :beef, cheese:, onions: true, bacon: false)

...
order_burger("Grimm", cheese: false, onion: false)
# ~> -:11:in `<main>': unknown keyword: onion (ArgumentError)

187 More Keyword Arguments

★

2 more advanced use cases

def order_meal(customer_name, fries: true, drink: "cola", **options)
  order_burger(customer_name, options)

cheeseをtrueにするラッパー

def order_cheeseburger(customer, **options)
  order_burger(customer, cheese: true, **options)

188 More Keyword Arguments

★

Jim Weirich

he was a RubyTapas viewer
Today's episode is about one of the ideas he sent me in that email.

alias of raise

fail "Abandon ship!"

most of the Ruby world has embraced #raise over #fail

Not Jim Weirich, though—in his projects, he used both methods

When indicating a failure for the first time, he would use fail.

use raise when re-raising an exception

I'm a big fan of conventions that give extra semantic information to code readers. Lately I've started to use this one in my own code