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Ruby Cheatsheet

String

puts "This is a string. \r\n".chomp
puts "   word  ".chomp
puts "word".chomp
puts "word".chop
puts "word \r\n".chop
puts "   word  \r\n".strip

switch case

Case uses ===, which means subsumption. "If I have a drawer labeled a would it make sense to put b in that drawer?"

puts (1..5) === 3
puts (1..5) === 6
puts Integer === 1
puts Integer === "ADIOASJDAS"
obj = 1
puts obj.class
case obj
when Fixnum
  puts "It's Fixnum"
when String
  puts "It's String"
else
  puts "It's somehing else"
end

lambda and Proc

Two differences:

  1. lambda checks the arguments
  2. lambda returns the value of the lambda, but Proc returns from the enclosure block
l = lambda {|a, b| a**2 + b**2 }
l.call 1, 2     # 5
l.call 1, 2, 3  #ArgumentError: wrong number of arguments (3 for 2)
p = Proc.new {|a, b| a**2 + b**2}
p.call 1, 2     # 5
p.call 1        # NoMethodError: undefined method `**' for nil:NilClass
lambda { return :foo }.call # => :foo
return # => LocalJumpError: unexpected return
Proc.new { return :foo }.call # => LocalJumpError: unexpected return

Cheatsheet of Rails Development

Basics

Create app

rails new sample_app

Generate controller

rails generate controller Users new

Generate model

rails generate model User name:string email:string

Add index to column

rails generate migration add_index_to_users
class AddIndex < ActiveRecord::Migration[6.0]
  def change
    add_index :users, :email, unique: true
  end
end

Generate integration test

rails generate integration_test users_signup

Migration

rails db:migrate
rails db:migrate:reset #run all the migrations
rails db:reset  # drop create seed
rails db:rollback STEP=2

Deployment

heroku

heroku create
git push heroku
heroku login --interactive
git push heroku
heroku run rails db:migrate
heroku run rails console --sandbox

SSL

Rails.application.configure do
  config.force_ssl = true
end

Puma configuration

max_threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
min_threads_count = ENV.fetch("RAILS_MIN_THREADS") { max_threads_count }
threads min_threads_count, max_threads_count
port        ENV.fetch("PORT") { 3000 }
environment ENV.fetch("RAILS_ENV") { ENV['RACK_ENV'] || "development" }
pidfile ENV.fetch("PIDFILE") { "tmp/pids/server.pid" }
workers ENV.fetch("WEB_CONCURRENCY") { 2 }
preload_app!
plugin :tmp_restart

Helper

flash

flash.now[:success] = "Welcome"
flash.now[:danger] = "Error"
<% flash.each do |message_type, message| %>
  <%= content_tag(:div, message, class: "alert alert-#{message_type}") %>
<% end %>

Bootstrap

yarn add jquery@3.5.1 bootstrap@3.4.1

config/webpack/environment.js

const { environment } = require('@rails/webpacker')
const webpack =require('webpack')
environment.plugins.prepend('Provide',
  new webpack.ProvidePlugin({
    $: 'jquery/src/jquery',
    jQuery: 'jquery/src/jquery',
    Popper: ['popper.js', 'default']

  })
)
module.exports = environment

app/javascript/packs/application.js

require("@rails/ujs").start()
require("turbolinks").start()
require("@rails/activestorage").start()
require("channels")
import "bootstrap"

app/assets/stylesheets/application.scss

@import "bootstrap";