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Design patterns (in Ruby)

Design patterns are just tools that help us constructing a software.

Template Method pattern

In the Template Method pattern, we create a skeletal class and it is basis for various subclasses or concrete classes. Within in the skeletal class, there are abstract methods, which in turn, will be overridden by the methods of subclasses.

Let's take an example of simple payment system,

Rails mailer structure

Your application is growing, and you are starting to have a complex mailing system: notification emails, retention emails, misc user emails, admin emails, etc...

It's time to clean up your mailers !

Existing mailer

You may already have a single mailer, responsible of every emails, like this one:

tmux cheat sheet

(C-x means ctrl+x, M-x means alt+x)

Prefix key

The default prefix is C-b. If you (or your muscle memory) prefer C-a, you need to add this to ~/.tmux.conf:

remap prefix to Control + a

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

OS X Screencast to animated GIF

This gist shows how to create a GIF screencast using only free OS X tools: QuickTime, ffmpeg, and gifsicle.

Instructions

To capture the video (filesize: 19MB), using the free "QuickTime Player" application:

Each of these commands will run an ad hoc http static server in your current (or specified) directory, available at http://localhost:8000. Use this power wisely.

Discussion on reddit.

Python 2.x

$ python -m SimpleHTTPServer 8000

	module Destroyable
	def call_destructor(id)
	@destructors[id].each do \|o\|
	o.__destroy(id) if o.respond_to? :__destroy
	end
	@destructors.delete(id)
	end

	def is_destroyable
	@destructors = {}

	class Foo
	attr_reader :bar
	def initialize
	@bar = 123
	ObjectSpace.define_finalizer( self, self.class.finalize(bar) )
	end

	def self.finalize(bar)
	proc { puts "DESTROY OBJECT #{bar}" }
	end

	require 'rails_helper'

	RSpec.describe TodosController, :type => :controller do

	context "GET index" do
	#context "POST create" do
	#context "GET show" do
	#context "PATCH update" do (or PUT update)
	#context "DELETE destroy" do
	#context "GET new" do

	=Navigating=
	visit('/projects')
	visit(post_comments_path(post))

	=Clicking links and buttons=
	click_link('id-of-link')
	click_link('Link Text')
	click_button('Save')
	click('Link Text') # Click either a link or a button
	click('Button Value')