ActiveRecord::Type::Boolean.new.cast('true') # => true
ActiveRecord::Type::Boolean.new.cast('false') # => false

module ActiveModel
  module Type

    ...
    class Boolean < Value
      FALSE_VALUES = [
        false, 0,
        "0", :"0",
        "f", :f,
        "F", :F,
        "false", :false,
        "FALSE", :FALSE,
        "off", :off,
        "OFF", :OFF,
      ].to_set.freeze

      ...
      private
        def cast_value(value)
          if value == ""
            nil
          else
            !FALSE_VALUES.include?(value)
          end
        end
    end
  end
end

ActiveRecord::Type::Boolean.new.cast('0') # => false
ActiveRecord::Type::Boolean.new.cast(0) # => false
ActiveRecord::Type::Boolean.new.cast('false') # => false
ActiveRecord::Type::Boolean.new.cast("FALSE") # => false
ActiveRecord::Type::Boolean.new.cast("off") # => false
ActiveRecord::Type::Boolean.new.cast("OFF") # => false

ActiveRecord::Type::Boolean.new.cast('1') # => true
ActiveRecord::Type::Boolean.new.cast(1) # => true
ActiveRecord::Type::Boolean.new.cast('true') # => true
ActiveRecord::Type::Boolean.new.cast('TRUE') # => true
ActiveRecord::Type::Boolean.new.cast('on') # => true
ActiveRecord::Type::Boolean.new.cast('ON') # => true

ActiveRecord::Type::Boolean.new.cast('') # => nil
ActiveRecord::Type::Boolean.new.cast(nil) # => nil

class Utility
  def self.to_bool(value)
    ActiveRecord::Type::Boolean.new.cast(value)
  end
end

> Utility.to_bool('true')
true

class String
  def to_bool
    ActiveRecord::Type::Boolean.new.cast(self)
  end
end

> 'true'.to_bool
true

class Sample1
  def self.foo
    bar
  end

  private

    def bar
      puts 'bar'
    end
end

> Sample1.foo
Traceback (most recent call last):
1: from test.rb:13:in `<main>'
test.rb:3:in `foo': undefined local variable or method `bar' for Sample1:Class (NameError)

class Sample1
  def self.foo
    bar
  end

  private

    def self.bar
      puts 'bar'
    end
end

// エラーなく実行できる
> Sample1.foo
bar

// privateメソッドを呼べている
> Sample1.bar
bar

class Sample2
  class << self # クラスメソッドで定義
    def foo
      bar
    end

    private

      def bar # クラスメソッド内でprivateメソッドを定義する
        puts 'bar'
      end
  end
end

> Sample2.foo
bar

class Sample2
  def self.foo # クラスメソッドで定義
    bar
  end
  class << self

    private

      def bar # 特異クラス内でprivateメソッドを定義する
        puts 'bar'
      end
  end
end

> Sample2.foo
bar

import cycle not allowed

./app
├─ a/a.go
├─ b/b.go
├─ main.go
└─ go.mod

module app

go 1.19

package main

import (
  "app/a"
)

func main() {
  a.CallB()
}

package a

import (
  "fmt"
  "app/b"
)

func PrintA() {
  fmt.Println("A")
}

func CallB() {
  b.PrintB()
}

package b

import (
  "fmt"
  "app/a"
)

func PrintB() {
  fmt.Println("B")
}

func CallA() {
  a.PrintA()
}

% go run main.go
package command-line-arguments
        imports app/a
        imports app/b
        imports app/a: import cycle not allowed

<Text numberOfLines={1} ellipsizeMode="tail">
  abcdefghijklmnopqrstuvwxyz
</Text>

display: -webkit-box;
-webkit-box-orient: vertical;
-webkit-line-clamp: 3;
overflow: hidden;

## index.html

<style>
  select:invalid { color: #cdcdcd; } <!-- 先頭の項目の色 -->
  select option { color: black; } <!-- 通常の項目の色 -->
</style>

<select name="color" required>
  <option value="">色を選択して下さい</option>
  <option value="red">赤</option>
  <option value="blue">青</option>
  <option value="green">緑</option>
</select>

/* Your code... */

const Component = () => {
  return (
    <Select required={true}>
      <option value="">選択してください</option>
      <option value="red">赤</option>
      <option value="blue">青</option>
      <option value="green">緑</option>
    </Select>
  )
}

constSelect = styled.select`
  option {
    color:black;
  }
  :invalid {
    color: #cdcdcd;
  }
`

class SamplTaskWorker
 include Sidekiq::Worker
 sidekiq_options retry: 5

 def perform()
    # 処理
  end
end

$ SampleTaskWorker.new.perform

def perform()
  # 処理
  binding.pry
end

$ SampleTaskWorker.perform_async

version: '3'
services:
  mysql:
    image: mysql:5.7
    environment:
      MYSQL_DATABASE: development
      MYSQL_PASSWORD: password
      MYSQL_ROOT_PASSWORD: password
    # 文字化け対応
    command: mysqld --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci
    ports:
     - 3308:3306

$ docker-compose up

$ docker exec -it <MySQLのコンテナ名> bash

$ docker exec -it mysql bash

# mysql -u root -ppassword development

$ mysql -u <ユーザー名> -p<パスワード> -h <ホスト名> -P <ポート名> <DB名>

$ mysql -u root -ppawwrod -h 127.0.0.1 -P 3308 development

% git fetch

% git branch -r

% git checkout -b <ローカルでの表示ブランチ名> origin/<リモートのブランチ名>

% git checkout -b develop origin/develop