pdswan

waysToChange :: Int -> [Int] -> Int
waysToChange 0 _  = 1
waysToChange _ [] = 0
waysToChange amount denominations@(denomination:xs)
  | amount < 0 = 0
  | otherwise =
    (waysToChange (amount - denomination) denominations) +
    (waysToChange amount xs)

pdswan

module ActiveRecordScopeExtensions
  def self.union(left, right)
    active_record_klass = left.klass
    
    arel_union = [left, right].map do |scope|
      scope.select("#{active_record_klass.table_name}.id")
    end.reduce(&:union)
    
    temporary_table_name = TemporaryTableName.new([active_record_klass.table_name, "union"].join("_")).to_s
    active_record_klass.joins("INNER JOIN (#{arel_union.to_sql}) as #{temporary_table_name} ON #{temporary_table_name}.id = #{active_record_klass.table_name}.id")

pdswan

[3] pry(main)> ActiveRecordScopeExtensions.union(User.where(name: "Bob"), User.where(name: "Alice")).to_sql
=> "SELECT \"users\".* FROM \"users\" INNER JOIN (( SELECT users.id FROM \"users\"  WHERE \"users\".\"name\" = 'Bob' UNION SELECT users.id FROM \"users\"  WHERE \"users\".\"name\" = 'Alice' )) as users_union_b96cf9af7d77c501088feac76f259ba6 ON users_union_b96cf9af7d77c501088feac76f259ba6.id = users.id"

pdswan

[6] pry(main)> left = User.where(name: "Bill")
  User Load (0.9ms)  SELECT "users".* FROM "users" WHERE "users"."name" = $1  [["name", "Bill"]]
=> []
[7] pry(main)> $ left.union
Error: Couldn't locate a definition for left.union!
[8] pry(main)> left.respond_to?(:union)
=> true
[9] pry(main)> $ left.method_missing

From: /Users/pdswan/code/scratch/rails4_union/rails4/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.0/lib/active_record/relation/delegation.rb @ line 91:

pdswan

[14] pry(main)> left.arel.to_sql
=> "SELECT \"users\".* FROM \"users\" WHERE \"users\".\"name\" = $1"
[15] pry(main)> left.to_sql
=> "SELECT \"users\".* FROM \"users\" WHERE \"users\".\"name\" = 'Bill'"
[16] pry(main)>

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def run_spec(file)
  unless File.exist?(file)
    puts "#{file} does not exist"
    return
  end

  puts "Running #{file}"
  system "bundle exec rspec #{file}"
  puts
end

pdswan

*Response Headers*
Date	Wed, 04 Jan 2012 03:14:33 GMT
Server	Apache/2.2.3 (CentOS)
X-Powered-By	Phusion Passenger (mod_rails/mod_rack) 3.0.2
X-Runtime	0.976903
Status	500
Vary	Accept-Encoding,User-Agent
Content-Encoding	gzip
Content-Length	1267
Content-Type	text/html; charset=UTF-8

pdswan

git push heroku branch_name:master

pdswan

irb -r path_to_app.rb

pdswan

require 'test/unit'
require 'mocha'

# assumes MailingListUpdater is defined / exposed at the top level. this is not the case 
# for the code in this gist.

class MailingListUpdaterTest < Test::Unit::TestCase
  test "#update_mailing_list calls enqueue_for_mailing_list_update when a user is present" do
    user = mock('User', :enqueue_for_mailing_list_update => true)
    record = stub('Record')