Dissecting Ruby with Ruby

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Dissecting Ruby with Ruby @schneems

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@schneems

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Schnauser

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That man is married to Ruby, so to speak

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Ruby Me

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Python <3 ?

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Hans Peter Von Wolfe (the 5th)

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Sextant Gem

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Wicked ‘ ‘ Gem

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Triage Code codetriage.com

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Adjunct Professor

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Good News Everyone! schneems.com/ut-rails

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We optimize developer happiness

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Git Push: Deploy

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Ruby Task Force

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Ruby Task Force Member

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Co-worker

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Eat Naan Talk Ruby

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Eat Naan Talk Ruby

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Warning: I have Naan Jokes

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Some of them fall a bit “flat”

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Close your Laptops

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Unless you’re commenting on rails/rails issues

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We’ve all been there

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That comment is no longer valid “

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I have no Idea how it works, it just does. “

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Docs? Just look at the source code “

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Get in Get Info Get Around

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Get in

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$ bundle open wicked

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$ bundle open wicked

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Set Editor

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~/.bashrc export EDITOR="mvim"

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~/.bashrc export EDITOR="subl -w"

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$ echo $EDITOR subl -w

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Get Info Out

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Forget Fancy Debuggers

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All you need is “puts”

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Tracer Round

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puts “=================” Tracer Round

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Find the output

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puts “=================” Tracer Round

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puts “=================” Tracer Round Do you see it?

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How about now?

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A note on Notation

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String.new Class/Module

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String.new Method

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String.new class method

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Kernel#puts Not class method

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Caution!

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Nil

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Nil Null

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Nil Null Naan

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Obi-Naan Kenobi

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Who uses Ruby 2.0?

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Who uses Ruby 1.9.3?

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Who uses Ruby 1.8.7?

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Ruby 1.8.7 is End of Life-d in days

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try 2.0.0 or JRuby on heroku

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Get Around

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Let’s look at Ruby

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Where is this method used? Problem:

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Solution: Kernel#caller

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www. ruby-doc .org

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Wat?

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Kernel#caller gives you the back trace

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def self.order_by_issue_count puts caller.inspect self.order("issues_count DESC") end

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[ "~/projects/triage/app/controllers/pages_controller.rb:6:in `index'", "ruby/gems/actionpack-3.2.12/lib/action_controller/metal/implicit_render.rb:4:in "ruby/gems/actionpack-3.2.12/lib/abstract_controller/base.rb:167:in `process_act "ruby/gems/actionpack-3.2.12/lib/action_controller/metal/rendering.rb:10:in `proc "ruby/gems/actionpack-3.2.12/lib/abstract_controller/callbacks.rb:18:in `block i "ruby/gems/activesupport-3.2.12/lib/active_support/callbacks.rb:414:in `_run__37 "ruby/gems/activesupport-3.2.12/lib/active_support/callbacks.rb:405:in `__run_ca "ruby/gems/activesupport-3.2.12/lib/active_support/callbacks.rb:385:in `_run_pro "ruby/gems/activesupport-3.2.12/lib/active_support/callbacks.rb:81:in `run_callb "ruby/gems/actionpack-3.2.12/lib/abstract_controller/callbacks.rb:17:in `process "ruby/gems/actionpack-3.2.12/lib/action_controller/metal/rescue.rb:29:in `proces "ruby/gems/actionpack-3.2.12/lib/action_controller/metal/instrumentation.rb:30:i "ruby/gems/activesupport-3.2.12/lib/active_support/notifications.rb:123:in `bloc "ruby/gems/activesupport-3.2.12/lib/active_support/notifications/instrumenter.rb "ruby/gems/activesupport-3.2.12/lib/active_support/notifications.rb:123:in `inst "ruby/gems/actionpack-3.2.12/lib/action_controller/metal/instrumentation.rb:29:i File

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Use Kernel#caller

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Where is this method defined? Problem:

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Introducing My favorite super secret class

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Method

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Object#method

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> m = "hello world".method(:upcase) => #

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> m = "hello world".method(:upcase) => # > m.class => Method

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> m = "hello world".method(:upcase) => # > m.class => Method > m.call => "HELLO WORLD"

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Where is this method defined? Problem: (recap)

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Solution: Method#source_location

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$ cat app/models/user.rb class User < ActiveRecord::Base has_many :repo_subscriptions, dependent: :destroy has_many :repos, :through => :repo_subscriptions scope :public, where("private is not true") alias_attribute :token, :github_access_token def self.random order("RANDOM()") end #...

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$ rails c User.last.method(:github_url).source_location

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$ rails c User.last.method(:github_url).source_location =>["~/projects/triage/app/models/user.rb", 93]

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$ rails c User.last.method(:github_url).source_location =>["~/projects/triage/app/models/user.rb", 93] File

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$ rails c User.last.method(:github_url).source_location =>["~/projects/triage/app/models/user.rb", 93] Line Number

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Let’s see something real

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link_to in (rails) email templates needs a host set, but fails if you include http:// Problem:

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Fails config.action_mailer.default_url_options = { host: 'http://example.com' } http://http://example.com

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Works config.action_mailer.default_url_options = { host: 'example.com' } http://example.com

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let’s remove the http:// automatically, but how? Problem:

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How does that option get used?

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<% puts method(:link_to).source_location %>

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<% puts method(:link_to).source_location %> [“ruby/gems/actionpack-3.2.12/lib/action_view/helpers/ url_helper.rb” 231]

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$ bundle open $ bundle open actionpack

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def link_to(*args, &block) if block_given? options = args.first || {} html_options = args.second link_to(capture(&block), options, html_options) else name = args[0] options = args[1] || {} html_options = args[2] html_options = convert_options_to_data_attributes(options, html_options url = url_for(options) href = html_options['href'] tag_options = tag_options(html_options) href_attr = "href=\"#{ERB::Util.html_escape(url)}\"" unless href "#{ERB::Util.html_escape(name || url)}

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Enhance

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name = args[0] options = args[1] || {} html_options = args[2] html_options = convert_options_to_data_attributes(opt url = url_for(options) href = html_options['href'] tag_options = tag_options(html_options) href_attr = "href=\"#{ERB::Util.html_escape(url)}\"" "#{ERB::Util.html_escap

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Which url_for?

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13 matches 12 Files

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Method# source_location to the rescue

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name = args[0] options = args[1] || {} html_options = args[2] html_options = convert_options_to_data_attributes(opt puts “==============================” puts method(:url_for).source_location url = url_for(options) href = html_options['href'] tag_options = tag_options(html_options)

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puts “==============================” puts method(:url_for).source_location => [“actionpack-3.2.12/ lib/ action_view/helpers/url_helper.rb”, 100]

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def url_for(options = {}) options ||= {} case options when String options when Hash options = options.symbolize_keys.reverse_merge!(: super when :back controller.request.env["HTTP_REFERER"] || 'javasc else polymorphic_path(options) end end

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def url_for(options = {}) options ||= {} case options when String options when Hash options = options.symbolize_keys.reverse_merge!(: puts "===========================" puts self.class.ancestors super when :back controller.request.env["HTTP_REFERER"] || 'javasc else polymorphic_path(options) end end

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Module#ancestors

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“foo”.class.ancestors => [String, Comparable, Object, Kernel, BasicObject]

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puts "===========================" puts self.class.ancestors [#, #, ActionMailer::MailHelper ActionDispatch::Routing::RouteSet::MountedHelpers, #, ActionDispatch::Routing: ActionView::Base, Devise::OmniAuth::UrlHelpers, Devi WillPaginate::ActionView, WillPaginate::ViewHelpers, ActionView::Helpers, ActionView::Helpers::Translatio ActionView::Helpers::RecordTagHelper, ActionControll ActionView::Helpers::OutputSafetyHelper, ActionView: ActionView::Helpers::JavaScriptHelper, ActionView::H ActionView::Helpers::FormHelper, ActionView::Helpers ActionView::Helpers::DebugHelper, ActionView::Helper ActionView::Helpers::ControllerHelper, ActionView::H ActionView::Helpers::AtomFeedHelper, ActionView::Hel

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No content

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Too much Ruby?

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Solution: Moar Ruby

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Module#method_defined?

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"foo".class.method_defined?(:upcase) => true Module#method_defined?

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"foo".class.method_defined?(:upcase) => true 99.class.method_defined?(:upcase) => false Module#method_defined?

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Module#instance_method

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User.new.method(:github_url).source_location =>["~/projects/triage/app/models/user.rb", 93] User.instance_method(:github_url).source_location =>["~/projects/triage/app/models/user.rb", 93] Module#instance_method

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What were we doing?

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Right

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def url_for(options = {}) options ||= {} case options when String options when Hash options = options.symbolize_keys.reverse_merge!(:only puts "===========================" self.class.ancestors.each do |klass| next unless klass.method_defined?(:url_for) puts klass.instance_method(:url_for).source_locatio end super when :back controller.request.env["HTTP_REFERER"] || 'javascript else polymorphic_path(options)

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self.class.ancestors.each do |klass| next unless klass.method_defined?(:url_for) puts klass.instance_method(:url_for).source_location end ====================== actionpack-3.2.12/lib/action_view/helpers/url_helper.rb 100 actionpack-3.2.12/lib/action_view/helpers/url_helper.rb 100 actionpack-3.2.12/lib/action_view/helpers/url_helper.rb 100 actionpack-3.2.12/lib/action_dispatch/routing/url_for.rb 143

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====================== actionpack-3.2.12/lib/action_view/helpers/url_helper.rb 100 actionpack-3.2.12/lib/action_view/helpers/url_helper.rb 100 actionpack-3.2.12/lib/action_view/helpers/url_helper.rb 100 actionpack-3.2.12/lib/action_dispatch/routing/url_for.rb 143 One of these things is not like the others

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Almost Done (kinda)

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Quick Break:

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No content

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No content

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Back to your regularly scheduled broadcast

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Verify Caller def url_for(options = nil) puts "===========================" puts caller.inspect case options when String options when nil, Hash _routes.url_for((options || {}).symbolize_keys.rev else polymorphic_url(options) end end

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It checks out ============================ [“actionpack-3.2.12/ lib/ action_view/ helpers/ url_helper.rb:112:in `url_for'", # ...

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Follow the Source def url_for(options = nil) case options when String options when nil, Hash puts "===========================" puts _routes.method(:url_for).source_location _routes.url_for((options || {}).symbolize_keys.rev else polymorphic_url(options) end end

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action_dispatch/routing/route_set.rb:572 def url_for(options) finalize! options = (options || {}).reverse_merge!(default_url_options) handle_positional_args(options) user, password = extract_authentication(options) path_segments = options.delete(:_path_segments) script_name = options.delete(:script_name) path = (script_name.blank? ? _generate_prefix(options) : script_name.chomp('/') path_options = options.except(*RESERVED_OPTIONS) path_options = yield(path_options) if block_given? path_addition, params = generate(path_options, path_segments || {}) path << path_addition params.merge!(options[:params] || {}) ActionDispatch::Http::URL.url_for(options.merge!({ :path => path, :params => params, :user => user, :password => password })) end