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true and false vs. "truthy" and "falsey" (or "falsy") in Ruby, Python, and JavaScript

Many programming languages, including Ruby, have native boolean (true and false) data types. In Ruby they're called true and false. In Python, for example, they're written as True and False. But oftentimes we want to use a non-boolean value (integers, strings, arrays, etc.) in a boolean context (if statement, &&, ||, etc.).

This outlines how this works in Ruby, with some basic examples from Python and JavaScript, too. The idea is much more general than any of these specific languages, though. It's really a question of how the people designing a programming language wants booleans and conditionals to work.

If you want to use or share this material, please see the license file, below.

Update

mileer

class AddHstoreExtension < ActiveRecord::Migration
  def up
    execute 'CREATE EXTENSION hstore'
  end

  def down
    execute 'DROP EXTENSION hstore'
  end
end

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# Postgresql fancy datatypes!

* array
* hstore (=~ hash)
* json
* jsonb


  Philippe Creux - [@pcreux](http://twitter.com/pcreux)

mileer

namespace :db do
  namespace :enable do
    desc "enable hstore extension"
    task :hstore => [:environment, :load_config] do
      ActiveRecord::Base.connection.execute('CREATE EXTENSION IF NOT EXISTS hstore;')
    end
  end

  Rake::Task['db:schema:load'].enhance ['db:enable:hstore']
end

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# config/initializers/active_admin.rb

require 'active_admin_custom_filter'

ActiveAdmin.setup do |config|
  # ...
end

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Deploy Rails app to digitalocean with nginx, unicorn, capistrano & postgres

Create droplet of your liking (ubuntu 12.10 x32)

ssh to root in terminal with your server ip

ssh root@123.123.123.123

Add ssh fingerprint and enter password provided in email

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# This file extends and overrides parts of the ActiveAdmin DSL and internals
# in order to provide support for automatically displaying and editing images,
# which in our infrastructure are stored as URLs whose column names end in "img".
# Since this file will be reloaded frequently in the development environment,
# all operations done at load time (class_eval's, etc.) MUST be idempotent.

ActiveAdmin::Views::TableFor.class_eval do

  def img_column(col_sym=:img, title="Image")
    column title, sortable: false do |obj|

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  controller do
    ..
    def import
      @product = Product.find(params[:id])

      # access uploaded file - params[:file]

      # do the job

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Implement Routing for Subdomains

Rails 3.0 introduced support for routing constrained by subdomains.

A subdomain can be specified explicitly, like this:

match '/' => 'home#index', :constraints => { :subdomain => 'www' } 

mileer

<% if Rails.env.development? || Subdomain.new.internal_ip_user?(request) %>
  More verbose errors
<% end %>