Random Ruby (and Rails) Tips

Slides for Oedo Ruby Kaigi 04, presented on 19 April 2014.

http://regional.rubykaigi.org/oedo04/

Transcript

1. Random Ruby Tips and Rails 30
2. I Japan
4. Winston @winstonyw
6. ͔͜͜ΒӳޠΛ࢖͍·͢ɻ ͝ΊΜͳ͍͞ʂ
8. RubyAsia.com A fortnightly newsletter for Ruby news and articles from Asia
9. June 26 - 27, 2014 Singapore http://www.reddotrubyconf.com
10. SG Ruby Group http://www.meetup.com/Singapore-Ruby-Group/
14. Random Ruby Tips and Rails 30
15. Ruby Tips
16. >> "Hello World" => "Hello World” ! >> string = _ => "Hello World” ! >> string => "Hello World" #1 Underscore as Last Returned Value irb
17. >> n = 5000000 => 5000000 ! >> m = 5_000_000 => 5000000 ! >> n == m => true #2 Underscore as Separator irb
18. #3 Array Initialization Array(x).each do |x| puts x end if x.is_a? Array x.each { |x| puts x } else puts x end
19. #4 Hash Default >> hash = Hash.new(:default) ! >> hash[:not_found] => :default ! >> hash.fetch(:not_found) KeyError: key not found: :not_found irb
20. #5 Hash Fetch and Default >> hash = Hash.new ! >> hash.fetch(:not_found, :default) => :default ! >> hash.fetch(:not_found) {|e| "#{e} default"} => "not_found default" irb
21. Hash Map (1) >> hash.inject({}) do |new_hash, (k,v)| >> new_hash[k] = v*2 >> new_hash >> end => {:a => 2, :b => 4} irb Convert {a: 1, b: 2} To {a: 2, b: 4} #6
22. #7 Hash Map (2) >> Hash[hash.map{ |k,v| [k, v*2] }] => {:a => 2, :b => 4} ! >> hash.map{ |k,v| [k, v*2] } => [[:a, 2], [:b, 4]] ! >> Hash[[[:a, 2], [:b, 4]]] => {:a => 2, :b => 4} irb Convert {a: 1, b: 2} To {a: 2, b: 4}
23. #8 Hash Map (3) >> hash.merge(hash) { |key, oldval, newval| newval*2 } => {:a => 2, :b => 4} ! >> hash.merge(hash) { |_, _, newval| newval*2 } => {:a => 2, :b => 4} irb Convert {a: 1, b: 2} To {a: 2, b: 4}
24. #9 Case Conditions >> whichcase(1) => "I am an integer." >> whichcase("1") => "I am a string." >> whichcase(3) => "I am either 2 or 3." >> whichcase(4) => "I belong to a range." >> whichcase(8) => "I belong to a range." >> whichcase(20) => "I am 20!" >> whichcase(:nobody) => "I am nobody." irb def whichcase(num) case num when 1 "I am an integer." when "1" "I am a string." when 2, 3 "I am either 2 or 3." when 4..10 "I belong to a range." when ->(x) { x == 20 } "I am 20!" else "I am nobody." end end
25. >> %w(hello world).map { |s| s.upcase } => ["HELLO", “WORLD"] ! >> %w(hello world).map(&:upcase) => ["HELLO", "WORLD"] #10 Symbol to Proc to Block irb http://stackoverflow.com/questions/14881125/what-does-to-proc-method-mean
26. >> numbers = [1, 2, 3, 4] => [1, 2, 3, 4] ! >> numbers.inject(&:+) => 10 #11 Symbol to Proc to Block irb
27. >> %(hello world).map(&Star) >> ["** hello **", "** world **"] #12 Symbol to Proc to Block irb class Star def self.to_proc lambda { |x| "** #{x} **" } end end
28. #13 Exceptions Hierarchy def rescue_exception begin boom rescue Exception => e puts "Rescued: #{e}" end end Bad!!! Exception NoMemoryError ScriptError LoadError NotImplementedError SyntaxError SecurityError SignalException Interrupt StandardError ArgumentError EncodingError FiberError IOError IndexError KeyError StopIteration LocalJumpError NameError NoMethodError RangeError FloatDomainError RegexpError RuntimeError SystemCallError ThreadError TypeError ZeroDivisionError SystemExit SystemStackError fatal
29. #14 Rescue Refactoring def rescue_exception boom rescue NameError => e puts "Rescued: #{e}" end def rescue_exception begin boom rescue Exception => e puts "Rescued: #{e}" end end
30. Source Location #15 >> src = " ".method(:blank?).source_location => ["/vagrant/rails/activesupport/lib/active_support/ core_ext/object/blank.rb", 116] ! >> `subl #{src[0]}:#{src[1]}` ! >> " ".method(:slice).source_location => nil irb
31. $> ruby data.rb ! --> Read Data Position: 192 Hello World! --> Read Data Again Position: 192 Hello World! #16 Reading DATA in a Ruby File shell position = DATA.pos ! puts "--> Read Data" puts "Position: #{position}" puts DATA.read ! puts "--> Read Data Again" DATA.seek position puts "Position: #{position}" puts DATA.read ! __END__ Hello World!
32. $> echo "super\nsize\nme" | ruby -ne 'puts $_.upcase' SUPER SIZE ME #17 Command-line Ruby shell
33. $> ruby -run -e httpd . -p 8080 #18 Simple Ruby Server shell https://github.com/ruby/ruby/blob/trunk/lib/un.rb
34. >> require 'open-uri' ! >> big = open("http://localhost:8080/big.txt") => #<Tempfile ..> ! >> small = open("http://localhost:8080/small.txt") => #<StringIO ..> #19 OpenURI, Tempfile and StringIO irb 15KB 12Kb
35. >> OpenURI::Buffer::StringMax => 10240 ! >> OpenURI::Buffer.send :remove_const, 'StringMax' => 10240 ! >> OpenURI::Buffer.const_set 'StringMax', 0 => 0 #19 OpenURI, Tempfile and StringIO irb
36. >> require 'open-uri' ! >> big = open("http://localhost:8080/big.txt") => #<Tempfile ..> ! >> small = open("http://localhost:8080/small.txt") => #<Tempfile ..> #19 OpenURI, Tempfile and StringIO irb
37. #20 Singleton Module >> OneAndOnly.instance === OneAndOnly.instance => true ! >> OneAndOnly.new NoMethodError: private method `new' called for OneAndOnly:Class irb require 'singleton' class OneAndOnly include Singleton end http://www.ruby-doc.org/stdlib-2.1.1/libdoc/singleton/rdoc/Singleton.html
38. >> mq = MyQueue.new => #<MyQueue.. @q=[]> ! >> mq.enq(1) => [1] ! >> mq.enq(2) => [1, 2] ! >> mq.size => 2 ! >> mq.deq => 1 #21 Forwardable Module irb class MyQueue extend Forwardable ! def_delegator :@q, :push , :enq def_delegator :@q, :shift, :deq ! def_delegators :@q, :[], :size ! def initialize @q = [] end end http://www.ruby-doc.org/stdlib-2.1.1/libdoc/forwardable/rdoc/Forwardable.html
39. #22 Bundler Jobs $> time bundle install 78.55s user 21.97s system 17% cpu 9:20.32 total ! $> time bundle install -j4 83.05s user 23.84s system 54% cpu 3:16.18 total shell http://bundler.io/v1.5/whats_new.html
40. #23 Bundler Jobs Config $> cores=`sysctl -n hw.ncpu` $> bundle config --global jobs $((cores)) ! $> cat ~/.bundle/config —- BUNDLE_JOBS: ‘4’ shell http://bundler.io/v1.5/whats_new.html
41. #24 Bundler Commands $> bundle outdated # List installed gems with newer versions available ! $> bundle console # Opens an IRB session with the Gemfile pre-loaded shell http://bundler.io/v1.6/commands.html
42. Rails Tips
43. class AddNameToProducts < ActiveRecord::Migration def change add_column :products, :name, :string add_index :products, :name end end Migration Syntax #25 https://github.com/rails/rails/blob/master/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb $> rails generate migration create_product AddNameToProducts name:string:index shell
44. class AddCategoryIdToProducts < ActiveRecord::Migration def change add_reference :products, :category_id, index: true end end Migration Syntax #26 https://github.com/rails/rails/blob/master/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb $> rails generate migration create_product AddCategoryIdToProducts category_id:references shell
45. Sandboxed Console #27 $> rails console —-sandbox Any modifications you make will be rolled back on exit ! >> Product.all => #<ActiveRecord::Relation []> ! >> Product.create(name: “walkman") (0.0ms) SAVEPOINT active_record_1 SQL (1.7ms) INSERT INTO “products” ... (0.0ms) RELEASE SAVEPOINT active_record_1 => #<Product id: 1, name: “walkman"> ! >> exit (2.1ms) rollback transaction irb
46. Rake Notes #28 $> rake notes app/controllers/application_controller.rb: * [2] [TODO] remember to do this * [3] [FIXME] remember to fix this * [4] [OPTIMIZE] remember to optimize this irb class ApplicationController < ActionController::Base # TODO: remember to do this # FIXME: remember to fix this # OPTIMIZE: remember to optimize this end Uppercase Only! cd railsapp; rake -T
47. class UglyText def self.print puts <<-HERE I am not indented. But I am ugly on the inside. HERE end end Pretty Heredoc #29 >> UglyTest.print I am not indented. But I am ugly on the inside. irb
48. class NiceText def self.print puts <<-HERE.strip_heredoc I am not indented. And I look good on the inside. HERE end end Pretty Heredoc #29 >> NiceTest.print I am not indented. And I look good on the inside. irb
49. Question? #30 require 'active_support' ! class Winston cattr_writer :emotion def self.is ActiveSupport::StringInquirer.new(@@emotion) end end >> Winston.emotion = "happy" >> Winston.is.happy? => true irb
50. Sean Xie Dr. Khoo Chong Yee Teo Yinquan Teo Hui Ming Karthik T Credits
51. Thank You @winstonyw