RubyとRailsに入門する

a.each {|val| puts val}

a.each_with_index {|val, i| puts "#{val}, #{i}"}

a.push "Python"

a.pop
=> "Python"

a.unshift "C++"  #配列の先頭に要素を追加
a.shift          #配列の先頭の要素を抽出し元配列から削除
=> "C++"
a.delete("Java") #値を指定して削除
a.delete_at(1)   #インデックスを指定して削除
a.delete_if{|lang| lang.size >= 5} #条件指定して削除
a.clear          #配列の要素をすべて削除

a = [2, 33, 1, 3, 11, 22]
a.sort{|x,y| x.to_s <=> y.to_s}

a.sort do |x, y|
  x <=> y
end

irb(main):001:0> a = ["C++", "Ruby", "Python", "Java"]
=> ["C++", "Ruby", "Python", "Java"]
irb(main):002:0> a.size                     #配列の要素数
=> 4
irb(main):003:0> a.reverse                  #配列を逆転
=> ["Java", "Python", "Ruby", "C++"]
irb(main):004:0> a.find{|l| l.length == 4}  #最初に条件に合うものを検索
=> "Ruby"
irb(main):005:0> a.find_all{|l| l.length == 4} #条件に合うもの全て検索
=> ["Ruby", "Java"]
irb(main):006:0> a.map{|lang| lang * 2}     #配列の各要素の置き換え
=> ["C++C++", "RubyRuby", "PythonPython", "JavaJava"]
irb(main):007:0> b = ["Lisp", "Haskell"]
=> ["Lisp", "Haskell"]
irb(main):008:0> a + b                      #配列の連結
=> ["C++", "Ruby", "Python", "Java", "Lisp", "Haskell"]
irb(main):009:0> ["Ruby", "Java", "Ruby", "C++"].uniq #重複要素の除去
=> ["Ruby", "Java", "C++"]
irb(main):010:0> [nil, "Java", "Ruby", nil].compact  #nil要素の除去
=> ["Java", "Ruby"]

 h = {"John"=>40, "Paul"=>42}
 h = {John: 40, Paul: 42} #シンボルをキーとして生成
h.to_a      #キーと値のリスト

h.each{|k, v| puts "#{k}, #{v}"} #各キーと値の処理
h.each_key{|k| puts k}   #ハッシュの各キーに対する処理
h.each_value{|v| puts v} #ハッシュの各値に対する処理

h.has_key? "George"      #キーがあるか？
h.has_value? 40          #値があるか？

irb(main):001:0> h = {"John" => 40, "Paul" => 42, "Geroge" => 43}
=> {"John"=>40, "Paul"=>42, "Geroge"=>43}
irb(main):002:0> h.size       #ハッシュの要素数
=> 3
irb(main):003:0> h.empty?     #ハッシュが空かどうか？
=> false
irb(main):004:0> h.invert     #値からキーへのハッシュを返す
=> {40=>"John", 42=>"Paul", 43=>"Geroge"}
irb(main):005:0> h.sort       #ハッシュのキーでソートし配列で返す
=> [["Geroge", 43], ["John", 40], ["Paul", 42]]
irb(main):006:0> h2 = {"Ringo" => 40}
=> {"Ringo"=>40}
irb(main):007:0> h.merge h2   #ハッシュの内容をマージする（非破壊的）
=> {"John"=>40, "Paul"=>42, "Geroge"=>43, "Ringo"=>40}
irb(main):008:0> p h
{"John"=>40, "Paul"=>42, "Geroge"=>43}
=> {"John"=>40, "Paul"=>42, "Geroge"=>43}
irb(main):009:0> h.update h2  #ハッシュの内容をマージする（破壊的）
=> {"John"=>40, "Paul"=>42, "Geroge"=>43, "Ringo"=>40}
irb(main):010:0> p h
{"John"=>40, "Paul"=>42, "Geroge"=>43, "Ringo"=>40}
=> {"John"=>40, "Paul"=>42, "Geroge"=>43, "Ringo"=>40}

irb(main):001:0> t = Time.now                  #現在時刻を取得
=> 2012-01-23 01:23:45 +0900
irb(main):002:0> t.strftime("%Y/%m/%d %H:%M:%S") #時刻の書式化
=> "2012/01/23 01:23:45"
irb(main):003:0> t1 = Time.local(2012,1,1,0,0) #地方時で任意時刻を設定
=> 2012-01-01 00:00:00 +0900
irb(main):004:0> t2 = t1 + 3600                #3600秒後をt2に設定
=> 2012-01-01 01:00:00 +0900
irb(main):005:0> puts t2                       #t2はt1の1時間後に
2012-01-01 01:00:00 +0900
=> nil

irb(main):001:0> s = "apple   banana     orange"
=> "apple   banana     orange"
irb(main):002:0> s.scan(/\w+/)      #英数字の並びを抽出し配列に
=> ["apple", "banana", "orange"]
irb(main):003:0> s.split(/\s+/)     #スペースの並びを区切り文字とし配列に
=> ["apple", "banana", "orange"]
irb(main):004:0> s.gsub(/\s+/, ",") #スペースの並びをカンマに変換
=> "apple,banana,orange"

score = 80
result = score > 70 ? "Pass" : "Failed"  #右辺の評価結果をresultに代入
puts result

debug = true
num = 10
 
puts "num = #{num}" if debug  #debugがtrueのときのみ実行

数値.times {|変数|
  #処理
}

puts "upto:"
#numが3から5に1つずつ増加
3.upto(5) {|num|
  puts "num = #{num}"
}
 
puts "downto:"
#numが8から6に1つずつ減少
8.downto(6) {|num|
  puts "num = #{num}"
}
 
puts "step:"
#numが12.3から14.1を超える前まで0.5ずつ増加
12.3.step(14.1, 0.5) {|num|
  puts "num = #{num}"
}

lang = ["Ruby", "Java", "Python"]
 
for s in lang do
  puts s
end
 
for i in 1..3 do
  puts i
end

while 条件式 do
  #処理
end

begin
  #例外が発生するかもしれない処理
rescue 例外クラス => 例外オブジェクトを格納する変数 then
  #例外が発生したときの処理
else
  #例外が発生しなかったときの処理
ensure
  #例外の有無に関わらず最後に実行される処理
end

while str = STDIN.gets
  break if str.chomp == "exit"
  print "input text:", str
end

io = File.open(ファイル名, モード)
#ファイル処理
io.close

File.open(ファイル名, モード) do |io|
#ファイル処理
end

File.open("data.txt", "r") do |io|
  puts "---gets"
  p io.gets      #１行読み込んで表示
 
  puts "---readline"
  p io.readline  #１行読み込んで表示
 
  puts "---read"
  io.rewind      #読み込み位置を先頭に戻す
  p io.read(5)   #5バイト分読み込んで表示
  p io.read      #現在位置よりファイル全体を読み込んで表示
 
  puts "---readlines"
  io.rewind      #読み込み位置を先頭に戻す
  p io.readlines #ファイルの各行を要素とする配列を作成して表示
end

File.open("out.txt", "w") do |io|
  p io.puts  "AAAAA"  #文末に改行を入れて書き込む
  p io.print "BBBBB"  #文末の改行は付けずに書き込む
  p io.write "CCCCC"  #文末の改行は付けない。書き込んだバイト数を返す
end

File.join("C:/ruby", "data.txt")  #ファイルパスを連結
=> "C:/ruby/data.txt"

Dir.glob("C:/ruby/*.txt")  #ファイル一覧の取得
=> ["C:/ruby/out.txt", "C:/ruby/test.txt"]

session[:user_id] = user.id

@current_user = @current_user || User.find_by(id: session[:user_id])

@current_user ||= User.find_by(id: session[:user_id])

michael:
  name: Michael Example
  email: michael@example.com
  password_digest: <%= User.digest('password') %>

user = users(:michael)

cookies[:remember_token] = { value:   remember_token,
                             expires: 20.years.from_now.utc }

cookies.permenent[:remember_token] = remember_token

cookies.encrypted[:user_id] = user.id

class UsersController < ApplicationController
  before_action :logged_in_user, only: [:edit, :update]

  private
    def logged_in_user
      unless logged_in?
        flash[:danger] = "Please log in."
        redirect_to login_url, status: :see_other
      end
    end
end

def authenticated?(remember_token)
  return false if remember_digest.nil?
  BCrypt::Password.new(remember_digest).is_password?(remember_token)
end

def authenticated?(attribute, token)
  digest = self.send("#{attribute}_digest")
  return false if digest.nil?
  BCrypt::Password.new(digest).is_password?(token)
end

user.authenticated?(:remember, remember_token)

class Micropost < ApplicationRecord
  belongs_to :user
  validates :user_id, presence: true
  validates :content, presence: true, length: { maximum: 140 }
end

class User < ApplicationRecord
  has_many :microposts
  .
  .
  .
end

class Micropost < ApplicationRecord
  belongs_to :user
  default_scope -> { order(created_at: :desc) }
end

irb(main):001> a = Micropost.first
  Micropost Load (0.4ms)  SELECT "microposts".* FROM "microposts" ORDER BY "microposts"."created_at" DESC LIMIT ?  [["LIMIT", 1]]
=> nil

irb(main):002> User.count
  User Count (0.2ms)  SELECT COUNT(*) FROM "users"
=> 100
irb(main):003> User.first.microposts.count
  User Load (1.1ms)  SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT ?  [["LIMIT", 1]]
  Micropost Count (0.2ms)  SELECT COUNT(*) FROM "microposts" WHERE "microposts"."user_id" = ?  [["user_id", 1]]
=> 0

class ApplicationController < ActionController::Base
  include SessionsHelper

  private

    # ユーザーのログインを確認する
    def logged_in_user
      unless logged_in?
        store_location
        flash[:danger] = "Please log in."
        redirect_to login_url, status: :see_other
      end
    end
end

class CreateRelationships < ActiveRecord::Migration[7.0]
  def change
    create_table :relationships do |t|
      t.integer :follower_id
      t.integer :followed_id

      t.timestamps
    end
    add_index :relationships, :follower_id
    add_index :relationships, :followed_id
    add_index :relationships, [:follower_id, :followed_id], unique: true
  end
end

class User < ApplicationRecord
  has_many :microposts, dependent: :destroy
  has_many :active_relationships, class_name:  "Relationship",
                                  foreign_key: "follower_id",
                                  dependent:   :destroy
  .
  .
  .
end

Rails.application.routes.draw do
  # 略
  resources :users do
    member do
      get :following, :followers
    end
  end
  # 略
end

resources :users do
  collection do
    get :tigers
  end
end

Micropost.where("user_id IN (#{following_ids})
                 OR user_id = :user_id", user_id: id)
         .includes(:user, image_attachment: :blob)