Playing with Ruby on Rails

Here below are some notes I made while playing with Ruby and RoR. Interestingly, I found that RoR is a great way to learn about the foundations of web frameworks. I have a much stronger understanding about not just RoR, but of Django, Pyramid, and Web2Py. Every web framework really has the same few components (or some variation thereof): Models, Views, Controllers, and Routes.

I walked through the free tutorial by CodeSchool:

The Basics:

CRUD
Create,Read,Update,Destroy

Zombie.new
z = Zombie.new(initialize)
z.save
Zombie.create
Zombie.find(3)
Zombie.update_attributes

Models:

class Tweet < ActiveRecord::Base (just means that class Tweet inherits from ActiveRecord)
end

validate data before it is saved in DB

class Tweet < ActiveRecord::Base
    validates_presence_of :status
end

t.errors -> returns errors
t.errors[:status] --> just error pertaining to status

Rails 3 new syntax for validation:

validates attribute, validation
validates :status, :presence => true
validates :status, :length => {:minimum => 3}

app/models/tweet.rb

class Tweet < ActiveRecord::Base
    belongs_to :zombie
end

app/models/zombie.rb

class Zombie < ActiveRecord::Base

    has_many :tweets

end

View:

web request -> 4 layers -> models, view, controllers, routing

<%...%> evaluate ruby

<%=...%> evaluate and print results

layouts/application --> make html page format and use <%= yield %>

/app/views/tweets/shot.html.erb (code that will be yielded is in here)

Adding CSS

<%= stylesheet_link_tag :all %>

<%= javascript_include_tag :defaults %> # can replace prototype javascript library with jquery

<%= csrf_meta_tag %> #protects website from hackers

with URLs, it checks public folder first, then tries to execute inside rails

Adding a Link

<%= link_to "link text",  "link path (URL)"%>

<%= link_to tweet.zombie.name, zombie_path(zombie.tweet) %>

<%= link_to "Edit", edit_tweet_path(tweet) %>

<%= link_to "Delete", :method => :delete %>

Listing Zombies

Listing Tweets

<% Tweet.all.each do |tweet| %>

<% end %>

Status	Zombie
<% tweet.status %>	<% tweet.zombie.name %>

Controllers:

class TweetsController < ApplicationController

   def show

      @tweet = Tweet.find(params[:id]) #using an instance variable

       render :action => 'status' #for status.html.erb

       respond_to do |format|

          format.html #show html.erb

          format.xml  { render :xml => @tweet }

          format.json { render :json => @tweet }

   end

end

model calls goes into the controller files. All request data stored in a hash called params.

def index -> list all tweets

def show -> show a single tweet

def new -> show a new tweet form

def edit -> show an edit tweet form

def create -> create a new tweet

def update -> update a tweet

def delete -> delete a tweet

Authorization:

def edit

  @tweet = Tweet.find(params[:id])

   if session[:zombie_id] != @tweet.zombie_id

      flash[:notice] = "sorry, you can't edit this tweet"

      redirect_to(tweets_path)

    end

  end

 end

class TweetsController < ApplicationController

  before_filter :get_tweet, :only => [:edit, :update, :destroy]

  before_filter :check_auth, :only => [:edit, :update, :destroy]

  def get_tweet

    @tweet = Tweet.find(params[:id])

  end

def check_auth

  if session[:zombie_id] != @tweet.zombie_id

      flash[:notice] = "sorry, you can't edit this tweet"

      redirect_to(tweets_path)

  end

 end

Routing:

config/routes.rb

ZombieTwitter::Application.routes.draw do |map|

  resources :tweets #creates a "REST"ful resource

  match 'new_tweet' => "Tweets#new" # path => controller#action

  match 'all' => "Tweets#index", :as => "all_tweets" # now all tweets can be used as an object "link_to"

  match 'a' => redirect('/tweets')

  match 'google' => redirect('http://www.google.com')

  root :to => "Tweets#index"

  match 'local_tweets/:zipcode' => "Tweets#index"

  match 'local_tweets/:zipcode' => 'Tweets#index', :as => 'local_tweets'

end

<%= link_to "All Tweets", all_tweets_path %>

<%= link_to "Tweets in 32828", local_tweets_path(32828) %>