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Arel Cheatsheet on Steroids

A (more) complete cheatsheet for Arel, including NamedFunction functions, raw SQL and window functions.

Tables

posts = Arel::Table.new(:posts)
posts = Post.arel_table # ActiveRecord

Table alias

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PostgreSQL is Enough

• Simplify: move code into database functions
• Just Use Postgres for Everything
• Just use Postgres
• PostgreSQL is the worlds’ best database
• Postgres is eating the database world
• Hacker News discussion

Background and Cron Jobs

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! Hybrid Terminal Colours. Uses the palette from Tomorrow-Night:
! https://github.com/chriskempson/tomorrow-theme/blob/master/vim/colors/Tomorrow-Night.vim
! vim: ft=xdefaults

*background: #1D1F21
*foreground: #C5C8C6
! black
*color0: #282A2E
*color8: #373B41
! red

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macOS Setup Guide

TOC

1. automatic setup using ansible
2. install app form AppStore
3. configuration

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dismiss the popup notification

BetterTouchTool

-> Touch Bar Trigger Configuration
-> Apple Script
-> Run Apple Script (blocking)

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デフォルト値を持っているので、初期状態では出てこない。
画面上で on -> off してやると、値がでてくる。
このオプションを例に上げると:

1. before cmd 2) on -> off 3) aftercmd
   の結果を diff すると分かる。

$ defaults read > before

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#!/bin/bash -x

# https://developer.apple.com/library/archive/technotes/tn2450/_index.html
# https://qiita.com/hetima/items/b475997008dabd567da0

target=`hidutil list |grep 'Apple Internal Keyboard' |head -n 1 |awk 'BEGIN{printf "\{%s","\"VendorID\":"} {printf "%s",$1} {printf "%s",","} {printf "%s","\"ProductID\":"} END{printf "%s\}\n",$2}'`

# 0x700000000
# LeftControl=0xE0
LeftControl=0x7000000E0

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swift properties

https://docs.swift.org/swift-book/LanguageGuide/Properties.html

• ストアドプロパティ
  • Lazy Stored Property

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xcode:	11
target/platform:	iOS 13.1
swift:	5
warning:	'defer' statement before end of scope always executes immediately; replace with 'do' statement to silence this warning
fix-suggest:	Replace 'defer' with 'do'

func doSomething(value: Int?, value2: Int?) {
    guard let value = value else { return }

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sample code wandbox

eventfd is passing counting value.

eventfd_write(fd, 1);
-> read result: 1

eventfd_write(fd, 1);
eventfd_write(fd, 1);
-> read result: 2