Ruby 1.9.2 in Production with Tatsuhiro Ujihisa

(This is the presentation slides set for vancouver ruby meetup)

Before the talk...

• two questions
• easy one and normal one

Question 1

An easy Ruby quiz: How to define a method without using "def" keyword? (only with pure Ruby)

def a
  :something
end
p a #=> :something

Sample answer

self.class.module_eval do
  define_method(:a) do
    :something
  end
end
p a

Or

eval 'def a; :something; end'
p a

• There's no keyword def but string containing 'def'

I think there are a lot more answers

Question 2

A normal Ruby quiz: How to assign a value to a local variable without using assignment operator "="? (only with pure Ruby)

a = :something
p a #=> :something

Sample answer 1

for a in [:something]; end

p a

• "Local variable" is very special in Ruby
• Declaring a new local variable is completely static

One more answer which is only on 1.9

Sample answer 2

/(?<a>).*/ =~ ''
eval 'a=:something'

p a

There are a match operator =~ and a string which contains =, but no assignment operator =.

Ruby 1.9.2 in Production with Tatsuhiro Ujihisa

image

This talk contains

1. What is Ruby 1.9.2?
2. Differences between 1.8..1.9
3. Differences between 1.9.1..1.9.2
4. Differences between 1.9.2..1.9.3

The summary of this talk

"Ruby 1.9.2 makes your code cleaner and easier to maintain."

Ruby versions

• Ruby 1.8.6
  • Mar 2007
• Ruby 1.8.7
  • May 2008
• Ruby 1.9.0
  • Dec 2007
• Ruby 1.9.1
  • Jan 2009
• Ruby 1.9.2
  • Aug 2010

Ruby versions

• Ruby 1.8.6
  • Mar 2007
• Ruby 1.9.0
  • Dec 2007
  • Rails 2.0
• Ruby 1.8.7
  • May 2008
• Ruby 1.9.1
  • Jan 2009
• Ruby 1.9.2
  • Aug 2010
  • Rails 3.0

Background: Ruby versions

• All of them are officialy stable version
• But Ruby 1.9 series didn't look like stable

What's new?

• Which problems did 1.9 solved?
• How can you write code easily?
• -> Examples

Problems and solutions

• Verbose hash notation
• Difficulty in process handling
• etc..

Problem 1

About syntax

Problem 1

JSON is cool. Dictionary in Erlang is cool. Hash in Ruby is...?

JavaScript or Erlang:

{a: 1, b: 2, c: 3}

Ruby:

{:a => 1, :b => 2, :c => 3}

1.9.2 new Hash syntax

This solved the problem

Ruby:

{a: 1, b: 2, c: 3}

This issue mattered particularly in..

Haml, the tool everyone is using, needs a lot of hash.

HTML:

<img src="a.jpg" width="64" height="128"></img>

Haml with ruby variables:

%img{:src => icon_path, :width => icon[:width], :height => icon[:height]}

(the below doesn't work)

%img(src=icon_path width=icon[:width] height=icon[:height])

This issue mattered particularly in..

Using 1.9.2 new hash syntax

%img{src: icon_path, width: icon[:width], height: icon[:height]}

Problem 2

• About builtin methods

Problem 2

system or `` operator lacked some important functionalities.

• Ruby is a good shell script (Rakefile!),
• Ruby has some file/process handling methods,
• But..
  • You couldn't retrieve the output or error of system
  • You could run a command asynchronously with system with "&", but couldn't kill the process directly
  • You couldn't run a command asynchronously with ``

Example

Start a Sinatra app by a Ruby script and kill the app by the script

in shell script:

#!/bin/sh
ruby sinatra_app.rb &
PID=$!
# something...
kill $PID

in ruby?

Bad solution

system 'ruby sinatra_app &'

• You cannot get the proccess ID, so you cannot kill the process

Better solution

pid = fork do
  exec 'ruby', 'sinatra_app'
end
# something..
Process.kill 'KILL', pid

• This doesn't work on NetBSD4 or Windows due to fork()

Best solution

pid = spawn 'ruby', 'sinatra_app'
# something...
Process.kill 'KILL', pid

• :)
• spawn =~ {fork + exec} or {system + &}
• portable

New system and spawn spec

system({'A' => 'b'}, 'c', in: input_io, [:out, :err] => :out)
#=> true/false

spawn(...)
#=> Fixnum

Even more..

open3 standard library

• Open3.capture2e
• powered by spawn (read the source!)

Problem 3

• Local variable shadowing (potantial bug!)

  a = :hello
  [1, 2, 3].each do |a|
    p a
  end
  p a #=> 3 (in 1.8)
  

Problem 4

• "Most libraries didn't work"
• Yes it was (particularly on 1.9.1)

now?

Active libraries work for sure!

• nokogiri
• rails

Problem 5

Installation

• install ruby, and then install rubygems, ...

rubygems is builtin!

• rake as well

Problem 6

Ruby is slow

YARV!

fib 31

• 1.8.7
  • 7.99sec
• 1.9.2
  • 0.64sec
• (jruby)
  • 3.00sec

How to make legacy code 1.9 compatible?

Changes between 1.8 and 1.9

• String isn't Enumerable
• when clause doesn't accept colon as semicolon

change between 1.9.1 and 1.9.2

• $: doesn't have the current dir.
  • require_relative is handy (but long...)

Demo: make a gem library 1.9.2 compatible

• github gem library
• github create etc..
• it's very 1.8 even though it's new
  • 0.1.0 was March 3, 2008
  • 0.4.5 was Oct 25, 2010; after 1.9.2 public release!

The summary of this talk (again)

"Ruby 1.9.2 makes your code cleaner and easier to maintain."

end

thanks!

by

• Tatsuhiro Ujihisa
• @ujm
• HootSuite Media, inc
• Ruby, Haskell, JavaScript, Vim script, etc..

hootsuite

appendix

• JRuby
  • --1.9 option
  • almost compatible with 1.9 except spawn() or etc