Olivier JM Maniraho OlivierJM

Rails Migration

http://guides.rubyonrails.org/migrations.html

Migrations methods:

add_column
add_index
change_column
change_table
create_table
drop_table

Originally published in June 2008

When hiring Ruby on Rails programmers, knowing the right questions to ask during an interview was a real challenge for me at first. In 30 minutes or less, it's difficult to get a solid read on a candidate's skill set without looking at code they've previously written. And in the corporate/enterprise world, I often don't have access to their previous work.

To ensure we hired competent ruby developers at my last job, I created a list of 15 ruby questions -- a ruby measuring stick if you will -- to select the cream of the crop that walked through our doors.

What to expect

Candidates will typically give you a range of responses based on their experience and personality. So it's up to you to decide the correctness of their answer.

Accumulate values by key from an array of objects (key/value mappings):

records = [
  { a: 10, b: 20, c: 30 }, 
  { a: 11, b: 21 }, 
  { a: 12, b: 22, c: 32, d: 42 }
]

pivoted = pivot(records)

How do you POST a JSON file with curl??

You can post a json file with curl like so:

curl -X POST -H "Content-Type: application/json" -d @FILENAME DESTINATION

so for example:

	# Doesn't work
	<p>
	<% case @request.author_hosted %>
	<% when "yes" %>
	The school <b>has</b> hosted an author before.
	<% when "no" %>
	The school <b>has not</b> hosted an author before.
	<% end %>
	</p>

	# Aliases
	alias g='git'
	compdef g=git
	alias gst='git status'
	compdef _git gst=git-status
	alias gl='git pull'
	compdef _git gl=git-pull
	alias gup='git fetch && git rebase'
	compdef _git gup=git-fetch
	alias gp='git push'

	var imageAddr = "http://www.tranquilmusic.ca/images/cats/Cat2.JPG" + "?n=" + Math.random();
	var startTime, endTime;
	var downloadSize = 5616998;
	var download = new Image();
	download.onload = function () {
	endTime = (new Date()).getTime();
	showResults();
	}
	startTime = (new Date()).getTime();
	download.src = imageAddr;

	# nil? can be used on any Ruby object. It returns true only if the object is nil.
	nil.nil? # => true
	[].nil? # => false
	{}.nil? # => false
	"".nil? # => false
	" ".nil? # => false
	true.nil? # => false

	# empty? can be used on some Ruby objects including Arrays, Hashes and Strings. It returns true only if the object's length is zero.
	nil.empty? # NoMethodError: undefined method `empty?' for nil:NilClass

	require 'nokogiri'
	require 'open-uri'

	# Get a Nokogiri::HTML:Document for the page we're interested in...

	doc = Nokogiri::HTML(open('http://www.google.com/search?q=tenderlove'))

	# Do funky things with it using Nokogiri::XML::Node methods...

	####

	# This command will list all table in a rails app in rails console

	ActiveRecord::Base.connection.tables