coursera-webapplications-002.md

Coursera Web Applications

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Modules 1 - 2 / Quizzes / Assignment

gem install bundler
gem install rails
rails new blog
cd blog
bundle exec rails server # or `bundle exec rails s`

At this point you can browse to your new rails webserver http://localhost:3000/.

Add scaffolding:

^C
bundle exec rails generate scaffold post title:string body:text
 # if the previous command hangs, look for a process `spring` and kill it
bundle exec rails generate scaffold comment post_id:integer body:text
bundle exec rails s

At this point you can browse to your new rails webserver http://localhost:3000/, but you'll see ActiveRecord::PendingMigrationError

^C
bundle exec rake db:migrate RAILS_ENV=development
bundle exec rails s

Then it should look OK: http://localhost:3000/

Set up BitBucket Account and blog repo

git remote add origin git@bitbucket.org:brian_cunnie/blog.git
git push -u origin --all # pushes up the repo and its refs for the first timegit push -u origin --tags # pushes up any tags

Module 3 / Quizzes / Assignment

To tie objects together with foreign keys, you need to add the following to the model:

• one-to-one: has_one, belongs_to
• many-to-one: has_many, belongs_to
• many-to-many: has_and_belongs_to_many (both)

Configure a Many-to-One Relationship

For example, to express a many-to-one relationship between comments and posts, do the following:

• edit app/models/post

class Post < ActiveRecord::Base
  has_many :comments, dependent: :destroy
end

(by the way, dependent: destroy is an associative hash that's passed as an argument to has_many)

• edit app/models/comment

class Comment < ActiveRecord::Base
  belongs_to :post
end

Nest Comments under Posts

To nest the comments under the posts, edit config/routes.rb:

Rails.application.routes.draw do
  resources :comments

  resources :posts do
    resources :comments
  end

Validate Data

We validate data in the models. For example, to make sure that every post has a title and a body, we edit app/models/post.rb:

class Post < ActiveRecord::Base
  has_many :comments, dependent: :destroy
  validates_presence_of :title, :body
end

Similarly for app/models/comment.rb:

class Comment < ActiveRecord::Base
  belongs_to :post
  validates_presence_of :post_id, :body
end

Submit Assignment

Submit assignments here: http://fdisk.co/mooc.

Observations

He consistently confuses forward-slash ("/") and backward-slash (""). Look at the screen—do not listen to him—when he uses the word "slash".

I will try do the exercises along with him the first time I listen to a lecture because I'll probably have to do them along with him later when I work on the assignment.

Module 3's assignment is Assignment 2, not Assignment 3.

Module 5 Assignment

Module 5's assignment is Assignment 3; don't let the inconsistent numbering scheme throw you off.

1. List Post's Comments

edit app/views/posts/show.html.erb and add the following:

 <h2>Comments</h2>
   <% @post.comments.each do |comment| %>
     <%= div_for comment do %>
     <p>
       <strong>Posted <%= time_ago_in_words(comment.created_at) %></strong><br />
       <%= h(comment.body) %>
     </p>
   <% end %>
 <% end %>

2. Create new comment form on Post's page

edit app/views/posts/show.html.erb and add the following:

<%= form_for([@post, Comment.new]) do |f| %>
  <p><%= f.label :body, "New Comment" %><br />
    <%= f.text_area :body %>
  </p>
  <p><%= f.submit "Add Comment" %></p>
<% end %>

We need to pass in the post's id so that the user isn't prompted to fill it out: edit app/controllers/comments_controller.rb and modify as follows:

def create
  @post = Post.find(params[:post_id])
  @comment = @post.comments.create(comment_params)
  
  respond_to do |format|
    if @comment.save
      format.html { redirect_to @post, notice: 'Comment was successfully created.' }

Now let's comment-out the [now unneeded] routes for comments. Edit config/routes.rb and comment-out the appropriate line:

Rails.application.routes.draw do
  #resources :comments

Remember to restart your rails server (you need to restart your rails server every time you change the routes).

3. Authentication

We need to add a before filter to our post's controller. Let's modify app/controllers/posts_controller.rb:

class PostsController < ApplicationController
  before_action :set_post, only: [:show, :edit, :update, :destroy]
  before_action :authenticate, except: [:index, :show]

Let's add an authenticate method in the private methods section of the controller:

def authenticate
  authenticate_or_request_with_http_basic do |name, password|
    name == "admin" && password == "secret"
  end
end

4. Test and Push

Test to make sure it works. Then push to your bitbucket repo:

git push origin head

5. Submit Assignment

Submit assignments here: http://fdisk.co/mooc.