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Code OptimizationsRuby

28 minutes

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Huh? What’s that?

Maintenance

•Simple•Extensible•Pertaining to the design principlesPerfo

rmance

•Speed•Memory

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Why would I want to do that?

Money Resources▪ Hardware▪ People (Developers)

Time▪ Speed of operation▪ Developer takes to figure out what’s going on

Karma

No one wants to write bad code!

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Ruby

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Interpolation over Concatenation

puts "This string embeds #{a} and #{b} through interpolation" # => faster

puts "This string concatenates " << a << " and " << b # => slower

puts "This string concatenates “ + a + " and " + b # => slower

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Destructive Operations!

hash = {}hash = hash.merge({1 => 2}) # duplicates the original hashhash.merge!({1 => 2}) # equivalent to previous line, and faster

str = "string to gsub"str = str.gsub(/to/, 'copy') # duplicate string and reassigns itstr.gsub!(/to/, 'copy') # same effect, but no object duplication

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Benchmark everything

require 'benchmark'

n = 100000Benchmark.bm do |x|

x.report('copy') { n.times do ; h = {}; h = h.merge({1 => 2}); end } x.report('no copy') { n.times do ; h = {}; h.merge!({1 => 2}); end }

end

# user system total real# copy 0.460000 0.180000 0.640000

(0.640692)# no copy 0.340000 0.120000 0.460000

(0.463339)

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Symbols whenever possible

'foo'.object_id # => 23233310'foo'.object_id # => 23228920

:foo.object_id # => 239298:foo.object_id # => 239298

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Array joins

[1, 2, 3] * 3 # => [1, 2, 3, 1, 2, 3, 1, 2, 3]

[1, 2, 3] * '3' # => "13233" 

%w{this is a test} * ", " # => "this, is, a, test" 

h = { :name => "Fred", :age => 77 }h.map { |i| i * "=" } * "\n" # => "age=77\nname=Fred"

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Everything is an object!

def add(adder, addee) adder + addeeend 

add(3,5) # => 8

class Fixnum def add(num) self + num endend

3.add(5) # => 8

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Use ranges instead of complex comparisons for numbers

# No more if x > 1000 && x < 2000 nonsense. Instead:

year = 1972puts case year when 1970..1979: "Seventies" when 1980..1989: "Eighties" when 1990..1999: "Nineties" end

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Ruby logic

def is_odd(x) if x % 2 == 0 return false else return true endend

def is_odd(x) x % 2 == 0 ? false : trueend

def is_odd(x) x % 2 != 0end

class Fixnum def odd? self % 2 != 0 endend

2.odd? # => false

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Enumerate single object

# [*items] converts a single object into an array. And if the object is an array, keeps it as it is.

[*items].each do |item| # ...end

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Rails

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Caching

Page Caching Fragment Caching Action Caching

Caching into Local / Instance Variable

# Makes a database query only if @current_user is nildef current_user @current_user ||= User.find(session[:user_id])end

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Don’t limit yourself to ActiveRecord

Use performance boosting database

features like:

Stored proceduresFunctionsX-query

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Finders are great but be careful

Retrieve only the information that you need. 

Don’t kill your database with too many queries. Use

eager loading.

Avoid dynamic finders like MyModel.find_by_*.

Need an optimized query? Run MyModel.find_by_sql.

# This will generates only one query,# rather than Post.count + 1 queriesfor post in Post.find(:all, :include => [ :author, :comments ]) # Do something with postend

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Control your controllers

Don’t let them become the God

classes.

Lesser instance variables.

Slimmer the better.

Appropriate code in appropriate

controller.

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And of course!

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Obey design principles.

Always code in context (Objects). It

is the best way to model your

solution.

Avoid “Quick and dirty”.

Understand that no good can ever

come out of duplication. Be it code,

design, data and most importantly

effort.

Simplicity is the key.

Enjoy coding!

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Slides

slideshare.net/ihower/rails-best-practices

slideshare.net/ihower/practical-rails2-350619

slideshare.net/preston.lee/logical-programming-with-ru

by-prolog

Ruby Books

The Ruby Way by Hal Edwin Fulton, Guy Hurst

The Rails Way by Obie Fernandez

Design Patterns in Ruby by Russ Olsen

Software Construction

Code Complete 2 by Steve McConnell

The Pragmatic Programmer: From Journeyman to Master by

Andrew Hunt