pengjunp

-- ex.1
SELECT isbn 
FROM editions 
INNER JOIN publishers ON editions.publisher_id = publishers.id 
WHERE publishers.name = 'Random House';

-- ex.2
SELECT editions.isbn, books.title 
FROM editions 
INNER JOIN publishers ON editions.publisher_id = publishers.id 

pengjunp

class Customer
  attr_reader :name, :budget
  def initialize(name, budget)
    @name = name
    @budget = budget
  end

  def within_budget?(price)
    price < budget
  end

pengjunp

class Comment
  attr_reader :user, :content, :post_id
  def initialize(user, content，post_id)
    @user = user
    @content = content
    @post_id = post_id
  end
end

pengjunp

# ex.1
require 'rubygems'
require 'rest-client'

wiki_url = "http://en.wikipedia.org/"
wiki_local_filename = "wiki-page.html"

File.open(wiki_local_filename, "w") do |file|
   file.write(RestClient.get(wiki_url))
end

pengjunp

class Person
  def self.example_class_method
    puts "We're calling an example class method"
    puts "'self' is always defined.  What is 'self' here?  Let's see."
    p self
    puts "That was self!"
  end

  def example_instance_method
    puts "We're calling an example *instance* method"

pengjunp

module Flight
  def Flight.fly(animal)
    if animal.superclass.name == "Bird" || name = animal.name == "Bat"
      "I'm a #{animal.name}, I'm flying!"
    end
  end
end

pengjunp

require 'rubygems'
require 'rest-client'

wiki_url = "http://en.wikipedia.org/"
wiki_local_filename = "wiki-page.html"

File.open(wiki_local_filename, "w") do |file|
   file.write(RestClient.get(wiki_url))
end

pengjunp

def count_letters (s)
  result = Hash.new(0)
  s.gsub(/\s/, "").each_char {|c| result[c] += 1}
  puts result.inspect
end

count_letters("This is a random string that doesn't make any sense at all")

def letter_indices (s)
  result = {}

pengjunp

def sign_price
  # declare the total price
  total = 0
  # calculate the size
  puts "Sign dimensions? length, width (feet)"
  dimensions = gets.chomp.split(',', 2)
  size = dimensions[0].to_f * dimensions[1].to_f
  total += 15 * size
  # calculate the colors
  puts "How many colors?"

pengjunp

Pry Cheat Sheet

• Youtube Tutorial 2013

Command Line

• pry -r ./config/app_init_file.rb - load your app into a pry session (look at the file loaded by config.ru)
• pry -r ./config/environment.rb - load your rails into a pry session

Debugger