Stop Reinventing The Wheel - The Ruby Standard Library

stop reinventing
the wheel
hidden gems in the ruby standard library

brian hogan - @bphogan

Twitter: @bphogan
Web: http://www.napcs.com/

What about this
design?
describe "the user" do
it "gets an email when their account is activated" do
# some stuff
end
end

Twitter: @bphogan

Sometimes ideas
evolve for the better.

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Other times not so
much.

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In software we
reinvent

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How often is
“better”
really just opinion?

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So, we’re not talking
about always using
what exists...

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We’re talking about
reinventing because
of ignorance, hubris,
or ego.

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Ruby Standard Library

http://ruby-doc.org/stdlib/

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•FileUtils
•Forwardable
•Pathname
•open-uri
•TempFile
•WEBrick

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Working With The File
System
system("mkdir -p tmp/files")
system("touch tmp/files/lockfile.lock")
system("rm -rf tmp/files")

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Make it platform-
independent!
require 'fileutils'

FileUtils.mkdir_p("tmp/files")
FileUtils.touch("tmp/files/lockfile.lock")
FileUtils.rm_rf("tmp/files")

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FileUtils
Namespace for several file utility methods
for copying, moving, removing, etc.

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Where it’s used

•Rake
•Capistrano stuff
•Sinatra Reloader gem
•Compass

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Where does it fall
short?

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Delegating Methods
Calling methods on one class through another.

User Proﬁle

name name

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Here’s how Rails
does it
def delegate(*methods)
options = methods.pop
unless options.is_a?(Hash) && to = options[:to]
raise ArgumentError, "Delegation needs a target.
Supply an options hash with a :to key as the last argument
(e.g. delegate :hello, :to => :greeter)."
end

methods.each do |method|
module_eval("def #{method}(*args, &block)
n#{to}.__send__(#{method.inspect},
*args, &block)nendn", "(__DELEGATION__)", 1)
end
end

Twitter: @bphogan

Here’s how Rails
does it
class User < ActiveRecord::Base
has_one :profile
delegate :name, :to => :profile
end

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Here’s how we could
do it.
require 'forwardable'

class User < ActiveRecord::Base
has_one :profile
extend Forwardable
def_delegator :profile, :bio, :bio
end

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Forwardable
This library allows you
delegate method calls to
an object, on a method by
method basis.

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Where it’s used

•MongoMapper
•Rack::Client

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Working with Paths

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Seen in tons of Rails
apps...
file = File.join(RAILS_ROOT, "config", "database.yml")
config = YAML.load(File.read(file))

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A better way
file = Rails.root.join("config", "database.yml")
config = YAML.load(file.read)

Rails.root.class
=> Pathname

http://litanyagainstfear.com/blog/2010/02/03/the-rails-module/

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Pathname
Library to simplify working
with ﬁles and paths.
Represents a pathname which locates a file
in a filesystem. The pathname depends on
OS: Unix, Windows, etc.

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Neat stuff
require 'pathname'
p = Pathname.new("/usr/bin/ruby")
size = p.size # 27662
isdir = p.directory? # false
dir = p.dirname # Pathname:/usr/bin
base = p.basename # Pathname:ruby
dir, base = p.split # [Pathname:/usr/bin, Pathname:ruby]

Twitter: @bphogan

Where it’s used

•Rails
•DataMapper
•Warehouse
•Webistrano
•many many more
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Grabbing Files

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cURL?
puts `curl http://pastie.org/1131498.txt?
key=zst64zkddsxafra0jz678g`

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Not available
everywhere,
must handle redirects.

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Treat URLs as ﬁles!
require 'open-uri'
url = "http://pastie.org/1131498.txt?key=zst64zkddsxafra0jz678g"
puts open(url).read

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open-uri

Wraps net/http, net/https, and net/ftp.

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Where it’s used

•Everywhere.

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Temporary ﬁles

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The hard way
path = "http://pastie.org/1131498.txt?key=zst64zkddsxafra0jz678g"
`curl #{path} > /tmp/template.html`
s = File.read("/tmp/template.html")
puts s

Twitter: @bphogan

Use TempFile
require 'open-uri'
require 'tempfile'
url = "http://pastie.org/1131498.txt?key=zst64zkddsxafra0jz678g"
tempfile = Tempfile.new("template.html")
tempfile.write open(url).read
puts tempfile.open.read

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Where it’s used

•File uploading
•Caching

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Data structures

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YAML loads to hashes
require 'YAML'
config = YAML.load(Pathname.new("config.yml").read)

puts config["company_name"]
puts config["banner_image_url"]
puts config["custom_css_url"]

Twitter: @bphogan

Use OpenStruct!
require 'ostruct'
require 'YAML'
config = YAML.load(Pathname.new("config.yml").read)
config = OpenStruct.new(config)
puts config.company_name
puts config.banner_image_url
puts config.custom_css_url

Twitter: @bphogan

Don’t write your own
“YAML-to-Object”
thing (like I once did!)

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Where it’s used

•Fat Free CMS
•ActiveMessaging
•Adhearsion
•AASM

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Watching Stuff

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Rails?

Twitter: @bphogan

def initialize
super
observed_descendants.each { |klass| add_observer!(klass) }
end

def self.method_added(method)
method = method.to_sym

if ActiveRecord::Callbacks::CALLBACKS.include?(method)
self.observed_methods += [method]
self.observed_methods.freeze
end
end

protected

def observed_descendants
observed_classes.sum([]) { |klass| klass.descendants }
end

def observe_callbacks?
self.class.observed_methods.any?
end

def add_observer!(klass)
super
define_callbacks klass if observe_callbacks?
end

def define_callbacks(klass)
existing_methods = klass.instance_methods.map { |m| m.to_sym }
observer = self
observer_name = observer.class.name.underscore.gsub('/', '__')

self.class.observed_methods.each do |method|
callback = :"_notify_#{observer_name}_for_#{method}"
unless existing_methods.include? callback
klass.send(:define_method, callback) do # def _notify_user_observer_for_before_save
observer.update(method, self) # observer.update(:before_save, self)
end # end
klass.send(method, callback) # before_save :_notify_user_observer_for_before_save
end
end
end
end
end

Twitter: @bphogan

Observer
Provides a simple
mechanism for one
object to inform a set of
interested third-party
objects when its state
changes.

Twitter: @bphogan

How we do it
require 'observer'

class ConfirmationEmailer
def update(account)
puts "Sending confirmation mail to: '#{account.email}'"
# send the email mechanism
end
end

Twitter: @bphogan

class Account
include Observable
attr_accessor :email, :active

def initialize(email)
self.email = email
self.active = false
add_observer ConfirmationEmailer.new
end

def activate_account!
self.active = true
changed # <- This is important
notify_observers self
end
end

Twitter: @bphogan

Serving Web Pages

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Sinatra?
require 'sinatra'
set :public, "~/Sites"

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How about this?
s = WEBrick::HTTPServer.new(:Port => 3000,
:DocumentRoot => "~/Sites")
trap('INT') { s.shutdown };
s.start

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How about an alias?
alias serve="ruby -rwebrick -e"s = WEBrick::HTTPServer.new(:Port => 3000, :DocumentRoot =>
Dir.pwd); trap('INT') { s.shutdown }; s.start""

$ cd ~/Sites
$ serve

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It also serves web
apps

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Your dev machine
really needs Passenger
running?

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Where it’s used

•Rails
•Other frameworks

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Storing Data

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PStore
Persistent, transactional
storage. Baked right in to
Ruby’s standard library.

Twitter: @bphogan

We can store stuff...
require 'pstore'
store = PStore.new('links')

links = %W{http://www.github.com
http://heroku.com
http://ruby-lang.org}

store.transaction do
store[:links] ||= []
links.each{|link| store[:links] << link}
store[:last_modified] = Time.now
end

Twitter: @bphogan

and we can get it
back.
store = PStore.new("links")
store.transaction do
links = store[:links]
end

puts links.join("n")

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Where it’s used

•Rails 1.x

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Where does it
fall short?

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Better Wheels

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Importing CSV ﬁles
require 'csv'

CSV.open('data.csv', 'r', ';') do |row|
p row
end

Twitter: @bphogan

CSV is slow.
“Use FasterCSV”

Twitter: @bphogan

In Ruby 1.9,
FasterCSV is the new
CSV!

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Working with Dates

Twitter: @bphogan

How we do it
today = DateTime.now
birthday = Date.new(2010, 10, 5)
days_to_go = birthday - today
time_until = birthday - today
hours,minutes,seconds,frac =
Date.day_fraction_to_time(time_until)

http://www.techotopia.com/index.php/Working_with_Dates_and_Times_in_Ruby

Twitter: @bphogan

home_run
home_run is an implementation of rubyʼs Date/
DateTime classes in C, with much better
performance (20-200x) than the version in the
standard library, while being almost completely
compatible.

http://github.com/jeremyevans/home_run

Twitter: @bphogan

REXML

Built-in library for
parsing and creating XML.

Twitter: @bphogan

How about
HPricot, libxml-
ruby, or
Nokogiri.
http://www.rubyinside.com/ruby-xml-performance-benchmarks-1641.html

Twitter: @bphogan

ERb

Templating language as part of the Standard Library.

Twitter: @bphogan

require 'erb'

template = ERB.new <<-EOF
<h1><%=@name %></h1>
EOF

@name = "AwesomeCo"

puts template.result

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Templating language
!=
View language!!!

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What can it do?

•Generate JavaScript
•Generate YAML
•Generate ERb
•Any type of proprietary data export

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Alternatives?

•HAML
•Liquid
•ERubis
•Tons of others

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Test::Unit

We have an awesome testing library
as part of our standard library.

Twitter: @bphogan

It’s pretty good.
Anyone know of any
alternatives?

Twitter: @bphogan

Only a few.
•RSpec
•Bacon
•Context / Contest / Shoulda / Matchy
•Testy
•Micronaut
•Whatever someone writes next week

Twitter: @bphogan

I use RSpec *

* And I still use Test::Unit.

Twitter: @bphogan

“Minitest is a minitest/unit
is a small and fast
replacement for ruby's
huge and slow test/unit”.

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If X sucks so bad, why
do we write
something else
instead of ﬁxing it?

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We think we can do it
better.

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The original developer
doesn’t want our help.

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There’s a language
barrier.

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Challenge:
Extend the Standard
Library.

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Make the wheels we
have better.

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That’s it.

•Twitter: @bphogan
•email: bphogan@gmail.com
•web: http://www.napcs.com/
•blog: http://bphogan.com
•github: http://github.com/napcs/
Twitter: @bphogan

Stop Reinventing The Wheel - The Ruby Standard Library

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