A small presentation explaining a limited set of good practices and code optimization techniques in Ruby and Ruby on Rails for beginners.

1. Code Optimizations Ruby 1 28 minutes

2. Huh? What’s that? 2

3. 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! 3

4. 4 Ruby

5. 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 5

6. Destructive Operations! hash = {} hash =hash.merge({1=>2}) # duplicates the original hash hash.merge!({1=>2}) # equivalent to previous line, and faster str="string to gsub" str=str.gsub(/to/, 'copy') # duplicate string and reassigns it str.gsub!(/to/, 'copy') # same effect, but no object duplication 6

7. Benchmark everything require 'benchmark' n =100000 Benchmark.bm do |x| x.report('copy') { n.timesdo ; h = {}; h =h.merge({1=>2}); end } x.report('no copy') { n.timesdo ; 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) 7

8. Symbols whenever possible 'foo'.object_id# => 23233310 'foo'.object_id# => 23228920 :foo.object_id# => 239298 :foo.object_id# => 239298 8

9. Array joins [1, 2, 3] * 3 # => [1, 2, 3, 1, 2, 3, 1, 2, 3] [1, 2, 3] * '3'# => "13233" %w{thisisatest} * ", " # => "this, is, a, test" h = { :name=>"Fred", :age=>77 } h.map { |i| i * "=" } * "" # => "age=77name=Fred" 9

10. Everything is an object! defadd(adder, addee) adder +addee end add(3,5) # => 8 classFixnum defadd(num) self+ num end end 3.add(5)# => 8 10

11. Use ranges instead of complex comparisons for numbers # No more if x > 1000 && x < 2000 nonsense. Instead: year =1972 puts case year when1970..1979:"Seventies" when1980..1989:"Eighties" when1990..1999:"Nineties" end 11

12. Ruby logic defis_odd(x) if x % 2==0 returnfalse else returntrue end end defis_odd(x) x % 2==0?false:true end defis_odd(x) x % 2!=0 end 12 classFixnum def odd? self % 2!=0 end end 2.odd? # => false

13. 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 13

14. 14 Rails

15. Caching Page Caching Fragment Caching Action Caching Caching into Local / Instance Variable 15 # Makes a database query only if @current_user is nil defcurrent_user @current_user||=User.find(session[:user_id]) end

16. Don’t limit yourself to ActiveRecord Use performance boosting database features like: Stored procedures Functions X-query 16

17. 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. 17 #This will generates only one query, # rather than Post.count + 1 queries for post inPost.find(:all, :include=> [ :author, :comments ]) # Do something with post end

18. Control your controllers Don’t let them become the God classes. Lesser instance variables. Slimmer the better. Appropriate code in appropriate controller. 18

19. 19 And of course!

20. 20 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!

21. 21 Slides slideshare.net/ihower/rails-best-practices slideshare.net/ihower/practical-rails2-350619 slideshare.net/preston.lee/logical-programming-with-ruby-prolog Ruby Books The Ruby Wayby Hal Edwin Fulton, Guy Hurst The Rails Way by Obie Fernandez Design Patterns in Rubyby Russ Olsen Software Construction Code Complete 2 by Steve McConnell The Pragmatic Programmer: From Journeyman to Masterby Andrew Hunt