ruby.md

Interactive Ruby Interface

• irb
• load file into IRB irb -r "./some_file.rb"
• irb> load ".some_file.rb"

Escape codes

\n
\t
\"
\'

answer = gets
p answer       # "enteredstring\n"

sprintf("%0.2f", @transaction[:amount].to_s)
ljust()
rjust()
clean_str = string.gsub("-", "")   # removes dashes
array.includes?

Math.sqrt(9)

Arrays

list = %w(milk eggs bread)    # ["milk", "eggs", "bread"]
item = "celery"
list = %W(#{item} bread)      # ["celery", "bread"]
puts list.inspect             # outputs list
.push and .unshift or += [] or <<
list.insert(2, "item")
list.includes?("celery")
list.drop(2)     # doesnt mutate gives last 2
list.slice(x,y)

arr = [1,2,3,4,7,88]
even_arr = arr.select { |item| item % 2 == 0 }
sml_arr = arr.reject { |item| item > 10 }
arr.inject(0) { |sum, element| sum += element }   # reduce

Classes

• instantiate str = String.new("some string") initialize method
• str.class = String
• str.methods.sort
• obj.respond_to? :method

module Tracking
  def create(name)
    object = new(name)
    instances.push(object)
    return object
  end
  def instances
    @instances || = []
  end
end

module SuperGroup
  def self.included(klass)
    klass.extend(Enumerable)
    attr_accessor :id, :count
  end
  def fetch(item)
    @count || = 0
    @count += 1
    puts "#{klass} count: #{@count}"
  end
end


class Group
  include Comparable
  #include Enumerable
  include SuperGroup
  extend Tracking
  attr_reader :name, :title
  attr_writer :name
  attr_accessor :desc

  def <=>(other_contact)
    name <=> other_contact.name
  end

  def each(&block)
    contacts.each(&block)
  end

  def initialize(name)
    @name = name
  end

  def name=(new_name)
    @name = new_name
    @conacts = []
  end
end  

Hashes

• new hash hash = {key: "val", key2: 33}
• hash[:key2]
• get all keys hash.keys
• contains a key `hash.has_key?("some_key")
• get value for key hash.fetch("some_key")
• add to has hash.store("new_key", new_val)
• contains a value hash.has_value?("value")
• get array of values hash.values_at("k1", "k2") # [val1, val2]
• for toString hash.inspect
• get the inverse hash.invert
• merge hash.merge(hash2)

Iterators

• times 5.times do |i|
• range for item in 1..10 do

Object methods

• show the available methods p "AA".methods.sort
• show the class p "AA".class gets String
• Duplicate an object Obj.dup

Convert types

str = "453"
int = str.to_i
float = "123.23".to_f

Rails

bin/rails generate scaffold NewClass field1:string field2:string
bin/rails db:migrate
bundle exec rake db:migrate

Files

append a file

File.open("somefile.txt", "a+") do |file|
end

Standard Library

• Date, Time
• hash = JSON.parse(somejson)
• json_str = JSON.dump(hash)
• JSON.load( File.new("./file.json") )
• str = YAML.dump(hash)
• hash = YAML.load(str)
• `hash = YAML.load_file("example.yml")``
• encoded = Base64.encode64(message)
• url_encoded = Base64.urlsafe_encode64(url)
• message = Base64.decode64(encoded)
• logger - Logger.new("log.txt")
• logger.info "some message"

Gems

• rubygems.org
• ruby-toolbox.com
• gem install [name of gem]
• gem list
• gem environment
• gem content [name of gem]

Creating a New Rails App

• gem install rails -v 3.2.16
• rails new digester --database=postgresql
• gem install activerecord-postgresql-adapter

Creating the Database

• In PSQL: create user digester with superuser
• ALTER USER digester WITH SUPERUSER
• \du \l
• rake db:create

Create Active Record Associations

• rails generate model Comment content:text name:string
• rails generate migration AddPostToComments post_id:integer:index
• Owner.first.pets.create(name: "Fluffy").save
• rails generate migration CreateJoinTableUsersForums users forums
• Uncomment index in ~_create_join_table_users_forums.rb
• rails generate model Profile user:references twitter:string github:string

erb

• <%= render partial: "comments/comment", collection: @post.comments, as: :comment %>
• <%= render @post.comments %> renders views/comments/_comment.html.erb

Rails Console

• bin/rails console
• get all records Someclass.all
• get most recent record Someclass.last
• get by ID 27 Someclass.where(id: 66)
• create new object employee = Employee.new
• delete record Employee.find(25).destroy

Rails Command

• bin/rails server
• bin/rails generate scaffold Post title:string
• bin/rails|rake db:migrate
• bin/rails generate migration AddBodyToPosts body:text
• rake db:migrate
• Get Routes rake routes for rails 3.2.16
• Controller generate|destroy rails generate controller Pages
• Model generate rails generate model Page title:string body:text slug:string
• bin/rails|rake db:migrate

References

• https://gist.github.com/mdang/95b4f54cadf12e7e0415
• https://teamtreehouse.com/library/has-one-associations