• https://rubyreferences.github.io/rubyref/

TODO

• https://github.com/wg/wrk
• learn WebSocket using ActionCable
• testing howto
• multi threading notes

Rails 8

1
2
3
4
5
6
7

# importmap + dartsass, NO hotwire
rails new myapp-sass \
  --asset-pipeline=propshaft --css=sass \
  --skip-action-mailbox --skip-action-text \
  --skip-hotwire --skip-jbuilder --skip-test --skip-system-test \
  --skip-bootsnap --skip-brakeman --skip-ci --skip-dev-gems \
  --devcontainer

• Rails.error.unexpected: report the given error when in production, or raise it when in development (for conditions not supposed to happen)
• ActiveRecord: rollback a DB transaction with raise ActiveRecord::Rollback
• ActiveRecord: stop callbacks chain (eg. validation) with throw :abort
• YJIT enable by default (must be compiled in ruby)
• Controller.rate_limit
• .devcontainer folder when creating a new app.
• default erb PWA files (manifest, service-worker) in app/views/pwa
• GitHub CI files for Dependabot, Brakeman, RuboCop, and running tests by default (--skip-ci)
• Brakeman by default for static analysis of security vulnerabilities (--skip-brakeman option)
• ActiveRecord::Base.with_connection
• allow_browser

• News { ActiveRecord | ActionView | ActiveJob | ActionCable | Frontend | Email | ActiveStorage | Security | Core | Devel | Tools&Gems | Testing | Info }

• Altro { Upgrade Exp. | References | Tools | Bench. | Books }

New in rails (till 2019-07-06)

⇑ ActiveRecord

• ActiveRecord::Relation#pick => .limit(1).pluck(*column_names).first
• Model errors as objects @ Rails >= 6.1
• ActiveRecord store wrapper around serialize to easily manage a hash value with attribute/keys methods accessors -- api, PR for dirty methods
• Model.optimizer_hints PR and Model.annotate PR
• leaverage DB unique constraints:
  • ActiveRecord's insert_all and upsert_all bulk insert/update methods leaveraging DB unique constraints -- PR, post
  • ActiveRecord#create_or_find_by -- relies on unique constrains, PR
• ActiveRecord's reselect, rewhere, reorder
• ActiveRecord enum attribute (int value by name) -- api
• Item.where(price: 10..) -- endless ranges in where conditions
• ActiveRecord::Base.verbose_query_logs = true: show the query source code line number
• multi-db support: suggestions, rake tasks per db, replica option/ro db
  • migrations path: PR1, PR2 -- define migrations_paths in database.yml
  • eileen slides
  • connects_to, connected_to switch DB connection PR; connected_to? check role and connection
  • rails db:schema:cache:dump, rails db:schema:cache:clear -- PR
  • fix query cache for multiple connections PR
  • Model.while_blocking_writes{} blocks/deny DB writes
• Change SQLite 3 boolean serialization from t/f to use 1/0 => migrate old data in DB
• Model#delegate_missing_to -- PR
• belongs_to new :default option -- es: belongs_to :person, default: -> {​ Person.current }
• ActiveRecord changes in callbacks: PR and reference table
• find_each{|r| ... } shortcut to find_in_batches{|b| b.each{|r| ... } }
  • also supports limit: Post.limit(10_000).find_each{​|p| ... }​
• DB comments
• db:migrate creates development and test databases
• migrations: sql expr as default value, es: t.datetime :published_at, default: -> { 'NOW()' }
• models derive from ApplicationRecord instead of ActiveRecord::Base
• ActiveRecord OR support, es: Post.where('id = 1').or(Post.where('id = 2'))
• after commit shortcuts:
  • ActiveRecord new callback after_save_commit = after_commit :hook, on: [ :create, :update ] -- PR
  • after_commit .. on: xxx shortcuts: after_xxx_commit -- xxx=create/update/destroy
• ActiveRecord Model.left_outer_joins support
• foreign keys now supported in create_table DSL
• Active Record ignored_columns -- no accessor methods and no show in queries
• multi context validations -- es: record.valid?(:ctx_name)
• People.in_batches(of: 100){|rel| rel.where... } -- vedi ActiveRecord::Relation#in_batches
• ActiveRecord.suppress -- silently disable record save in block (es: Model.suppress{...})
• Attributes API: define attr with a Proc, see commit (no more serialize misuse)
• DB connection pool explained here -- sqlite has no pool
  • Set database poolsize via RAILS_MAX_THREADS env
  • ActiveRecord::Base.connection_pool.stat -- status info hash
• find_in_batches got an end_at option
• active_record.warn_on_records_fetched_greater_than -- info

⇑ ActionView

• ActionText: rich text editor integrated with ActiveRecord and ActiveStorage (images/attachments)!! -- guide, intro
• ActionView helper current_page?
• form_with = form_for + form_tag: article, PR1, PR2
• new tag helpers -- es: tag.div(...)
• better controller's helpers proxy to use user defined helpers
• ActionController::Parameters#dig come per Hash#dig
• ActionDispatch Rails.application.reloader.wrap{} callback
• Per-form CSRF tokens -- config.per_form_csrf_tokens_enabled = false/true
• protect_from_forgery doen't run first anymore, it is simply queued as the other callbacks, use option prepend: true to set it as the first callback
  • NB: request_forgery_protection initializer removed from Rails --api because usually not needed
• controller/model's strong parameters
• controller actions default to head :ok if no template exists
• helpers div_for and content_tag_for will be gone in Rails 5 => recordtaghelper gem
• introduced the #{partial_name}_iteration local variable in partials rendered with a collection
• live streaming for persistent connections
• caching/faster rendering:
  • template dependencies with wildcard support
  • strong ETag -- Response#strong_etag=, weak_etag=, fresh_when, stale?
  • views cache control -- es: fresh_when
  • declarative etags

⇑ ActiveJob / background jobs

• ActiveJob -- interface for existing queuing systems
• vedi anche: ActionMailer#deliver_later, GlobalID
• retry_job, retry_on and discard_on catch multiple exceptions
• ActiveJob priority support
• config.active_job.queue_adapter = :async -- run jobs in threads a la sucker_punch
• queue_name_prefix -- PR

⇑ ActionCable / websockets

• ActionCable channel_prefix in your cable.yml
• ActionCable -- websockets: live features, chat, notifications | via redis or postgres
  • see ActionController::Renderer to render views, and use puma as a separate process in production

⇑ Frontend

• webpack integration: PR1, PR2 (make default), hp
• yarn javascript package manager used by default -- PR1, PR2, folders
• removed jQuery; vanilla UJS -- guide, jquery-rails, jquery-ujs
• turbolinks:
  • turbolinks 5 and 📺 railsconf video
  • moved to a separate repo
  • data-turbolinks-track="true" moved to data-turbolinks-track="reload"
• Sprockets gzip files
• Sprockets 4 upgrade -- source maps, manifest.js, ES6 support

⇑ Email

• ActionMailbox to process incoming emails -- guide
• Action Mailer Preprocessing -- eg: InvitationMailer.with(invitee: person).account_invitation.deliver_later, see also
• email previews
• ActionMailer rescue_from come nel controller

⇑ ActiveStorage / upload to cloud -- guide

• ActiveStorage/ActiveJob Mirror direct uploads
• include blob via Model.with_attached_columnname -- avoids N+1 query
• video/pdf preview
• custom previewers
• config.active_storage.routes_prefix = '/files' custom route prefix

⇑ Security & Paranoia

• MessageEncryptor -- enc/dec strings
• logger/inspect's per model attributes filter -- es: Model.filter_attributes = [:iban, :cf]
• config.action_dispatch.use_cookies_with_metadata = true -- Add Purpose/Name Metadata to Cookies to enhance security
• ActiveRecord.has_secure_password: you can specify the attribute name
• app-wide config.force_ssl deprecates ActionController#force_ssl
• new default headers X-Download-Options: noopen and X-Permitted-Cross-Domain-Policies: none
• Content-Security-Policy header DSL, moz ref -- disabled by default in 5.2
• credentials storage PR, guide -- rails credentials:edit
  • multi env support: config/credentials/production.yml.enc takes precedence over config/credentials.yml.enc, use rails credentials:edit --environment staging to edit specific file
  • secrets PR, guide -- eg: rails secrets:edit, rails secrets:show
• secure cookies server side enforced expire time -- es: cookies.signed[:user_name] = { value: "bob", expires: 2.hours }
• SSL exclude option: config.ssl_options = { redirect: { exclude: -> request { request.path !~ /healthcheck/ } } }
• Active Support's way to write to a file atomically (thread safe) with File.atomic_write

⇑ Core/config changes

• new Zeitwerk library loader: blog post, HP
• HTTP early hints/preloading
  • preload_link_tag helper: preload + http2 early hints
  • HTTP2 early hints, PR
• bootsnap installed by default -- TODO: crontab for periodic clean of tmp/cache
• routes: Custom url helpers and polymorphic mapping
• monkey patching is the past:
  • use ruby refinements instead of monkey patching
  • Deprecate alias_method_chain in favor of Module#prepend -- howto
• rails API mode: hp
• rake xxx:yyy tasks proxied by rails xxx:yyy
• config serve_static_files moved to public_file_server.enabled

⇑ Development

• rails console --sandbox don't write changes to DB -- PR+cfg
• byebug > 8.2.1 is faster
• faster dev reload: set in Gemfile group :development{gem 'listen', '~> 3.0.4'}

⇑ Tools / External gems

• Router Visualizer: PR, sample -- install graphviz dot command, run Rails.application.routes.router.visualizer and save the string to an html file
• ActiveRecord XML serialization moved in a gem
• Rails-observers -- separa le callbacks dai models/controllers
• ActiveResource -- consume json via rest

⇑ Testing

• Capybara Integration with Rails (AKA System Tests) -- with selenium and chrome, guide, parallel tests

⇑ Info / Minor changes / Good to know

• Array#extract! -- removes and returns the elements for which the block returns a true value (come select ma modifica la variabile)
• execjs: mini_racer replaces therubyracer
• rails notes custom tags -- PR
• rails notes task -- shows search code for FIXME/OPTIMIZE/TODO
• 📺 Rails 5 video tour by DHH on youtube
• rails new adds a default config/puma.rb
• String#parameterize per creare id ai titoli dei blog posts
• Array#inquiry.any?(:xxx) -- finds symbols and strings matching xxx
• locale yaml files auto-reloaded in development
• date and time:
  • DateTime.now.prev_occurring(:monday) -- PR
  • Date/Time #on_weekend? and #on_weekday? :D
  • Time vs DateTime -- commit
• Enumerable#pluck

⇑ Upgrade experiences -- google search

• kickstarter
• github
• ombulabs

⇑ References

• what's new: https://medium.com/rubyinside/whats-coming-to-rails-6-0-8ec79eea66da
• https://bogdanvlviv.com/posts/ruby/rails/what-is-new-in-rails-6_0.html
• -------------
• https://weblog.rubyonrails.org
• https://guides.rubyonrails.org/upgrading_ruby_on_rails.html
• https://edgeguides.rubyonrails.org/6_0_release_notes.html
• https://guides.rubyonrails.org/5_2_release_notes.html
• https://guides.rubyonrails.org/5_1_release_notes.html
• https://guides.rubyonrails.org/5_0_release_notes.html
• https://guides.rubyonrails.org/4_2_release_notes.html
• https://guides.rubyonrails.org

⇑ Tools

• scaling ruby apps
• 📺 DHH youtube videos on writing sw well
• MiniMagick
• ruby's set: a collection of unordered values with no duplicates
• obj.method(:method_name).source_location => mostra dov'e' definito il metodo
• <<~TAG ... TAG al poso di <<-TAG...TAG rimuove gli spazi di indentazione!
• thor -- build powerful command-line interfaces

⇑ Benchmark howto

docs, ips extension, article

1
2
3
4
5
6
7
8
9

require 'benchmark'

a = [:a, :b]
b = :b
n = 10000000
Benchmark.bm do |x|
  x.report { n.times do !(Array(a) & Array(b)).empty? end }
  x.report { n.times do Array(a).include?(b) end }
end

1
2
3
4
5
6
7
8

require 'benchmark/ips' # instructions per second
require 'uri'

uri = 'http://example.com/foos_json?foo=heyo'

Benchmark.ips do |x|
  x.report('URI.parse') { URI.parse(uri) }
end

vedi esempi di barnchmark in Hash#deep_merge PR

• StackProf hp, article

⇑ Books

• rails6 (beta)
• rails5 test

Note: YJIT is only available on arm64 and aarch64.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

apt install rustc           # needed by YJIT
apt install libjemalloc-dev # needed by jemalloc

# install
rvm install ruby-3.3.0 -C --with-jemalloc --enable-yjit

# jemalloc test 1
MALLOC_CONF=stats_print:true rvm 3.3.0 do ruby -e "exit"

# jemalloc test 2
ldd `which ruby` | grep jemalloc
#   => libjemalloc.so.2 => /lib/aarch64-linux-gnu/libjemalloc.so.2

# YJIT test
ruby --yjit -v
#   => ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [aarch64-linux]

# YJIT lazy loading:
ruby --yjit --yjit-disable -e "... ; RubyVM::YJIT.enable ; ..."

It's also possibile to apply jemalloc to a vanilla ruby:

1
2

# enable and test
LD_PRELOAD="libjemalloc.so.2" MALLOC_CONF=stats_print:true rvm 3.3.0 do ruby -e "exit"

Source: jemalloc @ stackoverflow.com, YJIT docs and RVM howto

Firefox user interface

From mozilla forum:

1. in about:config set toolkit.legacyUserProfileCustomizations.stylesheets = true
2. clone & install custom CSS from https://github.com/aris-t2/customcssforfx
3. uncomment @import "./css/tabs/tabs_below_navigation_toolbar_fx89.css";
4. cd firefox_profile && rm -rf chrome && ln -sf /path/to/repo/current

My about:config settings

• browser.download.alwaysOpenPanel = false -- fix naggin download panel since FF 98
• browser.tabs.loadDivertedInBackground = true @
• security.dialog_enable_delay = 100 @
• browser.tabs.hoverPreview.enabled = false @
• browser.tabs.hoverPreview.showThumbnails = false (Settings>General>Tabs) @

• set a custom user agent:

  1. Add new string value general.useragent.override
  2. Enter your preferred UA
  3. Check it on https://www.whatsmyua.info/

  This is especially useful if you are on an ARM device (like raspberry pi) and google keeps giving you its mobile version, for example:

  1 2	Mozilla/5.0 (X11; Linux armv7l; rv:60.0) Gecko/20100101 Firefox/60.0 # before Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0 # after

Add-ons

• auto reload tab
• awesome screenshot
• DeepL Translate -- store
• keepa amazon tracker
• pretty xml
• user agent switcher
• video download helper -- hp
• tampermonkey
• save page we

old:

• flash video downloader
• foxy proxy
• page translate
• unicode emoji
• simple tab renamer (attached)

Source: userChrome.org, CustomCSSforFx

Resolutions

• Sage: 1440x1920
• Glo: 758x1024

Developer mode / hidden settings

1. Type devmodeon in the searchbar, search and return to home screen
2. New menu entry apperars: Settings > Device Information > Developer options
3. Optional: type devmodeoff to disable it

NickelMenu / quick launcher

1. Download latest KoboRoot.tgz from home page/github
2. Connect Kobo to your PC
3. Put KoboRoot.tgz into KOBOeReader/.kobo
4. Eject your eReader and wait for it to reboot
5. Ensure there is a new menu item in the bottom-right main menu entitled NickelMenu
6. Connect Kobo to your PC again and create a file named KOBOeReader/.adds/nm/config, and follow the instructions in KOBOeReader/.adds/nm/doc to configure NickelMenu

Example:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42

menu_item :main    :Browser (fullscreen)  :nickel_browser     :
menu_item :main    :Browser (modal)       :nickel_browser     :modal

# KOreader: prevent Kobo from scanning hidden folders on 4.17+
# https://github.com/koreader/koreader/wiki/Installation-on-Kobo-devices#important-notes
# ==> append in ".kobo/Kobo/Kobo eReader.conf":
#   [FeatureSettings]
#   ExcludeSyncFolders=(\\.(?!kobo|adobe).+|([^.][^/]*/)+\\..+)
menu_item :main    :KOReader              :cmd_spawn          :quiet  :exec  /mnt/onboard/.adds/koreader/koreader.sh

menu_item :main    :Plato                 :cmd_spawn          :quiet  :/mnt/onboard/.adds/plato/plato.sh

menu_item :main    :Invert Screen         :nickel_orientation :invert
menu_item :main    :Sudoku                :nickel_extras      :sudoku
#menu_item :main    :Solitaire             :nickel_extras      :solitaire
#menu_item :main    :WordScramble          :nickel_extras      :word_scramble
#menu_item :main    :Dump Syslog           :cmd_spawn          :logread > /mnt/onboard/.adds/syslog.log

menu_item :main    :USB connect           :nickel_misc        :force_usb_connection
menu_item :main    :IP Address            :cmd_output         :500:/sbin/ifconfig | /usr/bin/awk '/inet addr/{print substr($2,6)}'
menu_item :main    :Telnet                :cmd_output         :500:quiet :/usr/bin/pkill -f "^/usr/bin/tcpsvd -E 0.0.0.0 2023"
  chain_success:skip:5
    chain_failure                         :cmd_spawn          :quiet :/bin/mount -t devpts | /bin/grep -q /dev/pts || { /bin/mkdir -p /dev/pts && /bin/mount -t devpts devpts /dev/pts; }
    chain_success                         :cmd_spawn          :quiet :exec /usr/bin/tcpsvd -E 0.0.0.0 2023 /usr/sbin/telnetd -i -l /bin/login
    chain_success                         :dbg_toast          :Started Telnet server on port 2023
    chain_failure                         :dbg_toast          :Error starting Telnet server on port 2023
    chain_always:skip:-1
  chain_success                           :dbg_toast          :Stopped Telnet server on port 2023
menu_item :main    :FTP                   :cmd_spawn          :quiet:/usr/bin/pkill -f "^/usr/bin/tcpsvd -E 0.0.0.0 1021" || true && exec /usr/bin/tcpsvd -E 0.0.0.0 1021 /usr/sbin/ftpd -w -t 30 /mnt/onboard
  chain_success                           :dbg_toast          :Started FTP server on port 1021.

menu_item :main    :Sleep                 :power              :sleep
#menu_item :main    :Reboot                :power              :reboot
menu_item :main    :Power Off             :power              :shutdown

menu_item :library :Import books          :nickel_misc        :rescan_books_full

menu_item :browser :Quit                  :nickel_misc        :home
menu_item :browser :Open modal            :nickel_browser     :modal
menu_item :browser :Invert Screen         :nickel_orientation :invert

menu_item :selection_search :WebSearch    :nickel_browser     :modal:https://duckduckgo.com/?q={1|S|%}

Notes: - FTP: user = root, pass = empty - Telnet: pass = none

KOReader / alternative reader, swiss knife

See the user guide and wiki, then follow install instructions:

1. Download the latest release from github
2. Connect Kobo to your PC
3. unzip -d /path/to/KOBOeReader/.adds/ koreader-kobo-v2023.04.zip

4. prevent Kobo from scanning hidden folders on 4.17+, append in .kobo/Kobo/Kobo eReader.conf:

   1 2	[FeatureSettings] ExcludeSyncFolders=(\\.(?!kobo|adobe).+|([^.][^/]*/)+\\..+)

5. add entry in NickelMenu, put in .adds/nm/config:

   1	menu_item :main :KOReader :cmd_spawn :quiet :exec /mnt/onboard/.adds/koreader/koreader.sh

6. Eject your eReader and enjoy

From the user guide a command to optimize images for the ereader with ImageMagick:

1
2
3
4
5
6

convert input-image.ext \
  -colorspace Lab -filter LanczosSharp -distort Resize 1404x1872 \
  -colorspace sRGB -background white -gravity center -extent 1404x1872! \
  -grayscale Rec709Luminance -colorspace sRGB \
  -dither FloydSteinberg -remap _eink_cmap.gif \
  -quality 75 output-image.ext

_eink_cmap.gif is also attached to this post.

Plato / alternative reader

See the forum thread and NickelMenu entry:

1. Download the latest release from github
2. Connect Kobo to your PC
3. mkdir /path/to/KOBOeReader/.add/plato
4. unzip -d /path/to/KOBOeReader/.adds/plato/ plato-0.9.36.7z
5. prevent Kobo from scanning hidden folders on 4.17+, see KOReader instruction above

6. add entry in NickelMenu, put in .adds/nm/config:

   1	menu_item :main :Plato :cmd_spawn :quiet :/mnt/onboard/.adds/plato/plato.sh

7. Eject your eReader and enjoy

Misc tools

• kepubify -- EPUB to KEPUB converter written in Go (standalone executable)

QOL settings

• full reference

• enable screenshots by pressing power button (saves a PNG in kobo root dir), append in .kobo/Kobo/Kobo eReader.conf:

  1 2	[FeatureSettings] Screenshots=true

• auto accept the Computer detected popup when plugged into a computer and enable devmodeon:

  1 2 3

  [DeveloperSettings] AutoUsbGadget=true EnableDebugServices=true

• random screensaver (sleep/poweroff):

  1. put images in .kobo/screensaver
  2. Settings > Energy saving and privacy > check Show current read and Show book covers full screen

• manual reset procedure: Sage, Glo

Bluetooth page turner

From reddit posts 1, 2:

1. buy a Ring Remote Control
2. install https://github.com/tsowell/kobo-btpt

3. config file .adds/.btpt/D01 Pro:

   1 2	nextPage EV_KEY KEY_NEXTSONG 0 prevPage EV_KEY KEY_PREVIOUSSONG 0

Signs that it's time to quit your job

1. You're not learning
2. You have a terrible boss
3. You're experiencing abuse
4. Your workplace is a toxic environment
5. Your feedback and ideas are not heard
6. You dread going to work in the morning
7. Your health is being negatively impacted
8. Your company seems financially unstable
9. You are being asked to do unethical things
10. You feel that there is no growth left for you
11. Your knowledge and skills are under-utilised
12. You have lost interest or passion for your job
13. There is a high turnover rate among employees
14. You get no feedback about your performance
15. Your responsibilities have increased, but the pay hasn't
16. You're consistently stressed, negative, or unhappy at work

Signs of a Bad Manager

1. Micromanagement: Constantly checking in on employees and not allowing autonomy
2. Poor Communication: Fails to provide clear instructions or feedback
3. Lack of Empathy: Shows no understanding or concern for employees' personal issues
4. Takes Credit for Others' Work: Does not acknowledge team contributions
5. Unapproachable: Creates an environment where employees feel they cannot voice concerns
6. Inconsistent: Changes decisions frequently and unpredictably
7. Lacks Vision: Does not have a clear direction or goals for the team
8. Plays Favorites: Gives preferential treatment to certain employees
9. Avoids Responsibility: Blames others for their own mistakes
10. Resists Change: Unwilling to adapt to new ideas or improvements