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Week 4 - Models

MVC

Rails is an MVC framework built on Ruby. MVC = Model, View Controller.

Controller (covered last week)

  • Facilitates control logic
  • Responsible to get the information from a server request and send them to a view to be rendered.
  • A bridge of communication between the models and views

Views (covered last week)

  • Presentation layer.
  • Templates that contain html and mixed with ruby code in order to present to the user the final response.

Models

  • Facilitates business logic
  • There are entities of your application that you will address using nouns, like users, tasks, etc.
  • Business logic that goes around these models entail the interactions around these things, their relationships and how they should work inside of the application.
  • This includes persistence, like saving data into the database.

Bookstore App

  1. Create a new rails app

    $ cd workspaces

$ rails _3.2.17_ new bookstore -T

$ cd bookstore

$ git add .

$ git init .

$ git commit -m "Initial commit"

    -T skips test unit

  2. Create a book model

    $ rails generate model Book name:string page_id:integer

  3. Look at generated files

    • comment out attr_accessible for the time being

  4. Migrate the database

    $ rake db:migrate

  5. Show db/schema.rb

  6. Check in changes

    $ git add .
$ git commit -m "Create book model"

  7. Rails console

    $ rails console
> book = Book.new
> book.name = "The Bible" # Didn't have to set up an attr_accessor because rails generates one for each column in db
> book.save # Now it's saved

> book_2 = Book.new name: "Charlie Brown", pages: 150

# Attr Accessible Error - Fix error
> reload!
> book_2 = Book.new name: "Charlie Brown", pages: 150
> book_2.save

> books = Books.all
> book = Book.find(2)

> book.name = "Calvin and Hobbes"
> book.save

> book.destroy

Taking it to the web

  1. Start server

    $ bundle exec rails s

  2. Visit /books (mention TDD flow)

  3. Create books route in config/routes.rb

    Bookstore::Application.routes.draw do
  get '/books' => 'books#index'
end

  4. Create app/controllers/books_controller.rb

    class BooksController < ApplicationController
end

  5. Create index method

    class BooksController < ApplicationController
  def index
  end
end

  6. Create app/views/books/index.html.erb

    <h1>Books</h1>

  7. Add html table of books

    In app/views/books/index.html.erb

    <h1>Books</h1>

<table>
  <tr>
    <th>Name</th>
    <th>Pages</th>
  </tr>
  <% @books.each do |book| %>
    <tr>
      <td><%= book.name %></td>
      <td><%= book.pages %></td>
    </tr>
  <% end %>
</table>

    In app/controllers/books_controller.rb

    class BooksController < ApplicationController
  def index
    @books = Book.all
  end
end

  8. Create a link to the bike detail page

    In app/views/books/index.html.erb

    <h1>Books</h1>

<table>
  <tr>
    <th>Name</th>
    <th>Pages</th>
  </tr>
  <% @books.each do |book| %>
    <tr>
      <td><%= link_to book.name, "books/#{book.id}" %></td>
      <td><%= book.pages %></td>
    </tr>
  <% end %>
</table>

  9. Create the show route

    Bookstore::Application.routes.draw do
  get '/books' => 'books#index'
  get '/books/:id' => 'books#show'
end

  10. Create the show action

    class BooksController < ApplicationController
  #index method

  def show
    @book = Book.find params[:id]
  end
end

  11. Create app/view/books/show.html.erb

    <h1><%= @book.name %></h1>

<p>Pages: <%= @book.pages %></p>

  12. Git commit

    $ git add .
$ git commit -m "Displaying books"

Creating Books

  1. Create a new link on the index page

    <%= link_to "New Book", "/books/new" %>

  2. Create a new deck route (routes are order specific)

    Bookstore::Application.routes.draw do
  get '/books' => 'books#index'
  get '/books/new' => 'books#new'
  get '/books/:id' => 'books#show'
end

  3. Create a new action in BooksController

    def new
  @book = Book.new
end

  4. Create app/views/books/new.html.erb

    <%= form_for @book do |f| %>
  <div>
    <%= f.label :name %>
    <%= f.text_field :name %>
  </div>
  <div>
    <%= f.label :pages %>
    <%= f.text_field :pages %>
  </div>
  <%= f.submit %>
<% end %>

  5. Create a POST create route

    Bookstore::Application.routes.draw do
  get '/books' => 'books#index'
  get '/books/new' => 'books#new'
  get '/books/:id' => 'books#show'
  post '/books' => 'books#create'
end

  6. Create a create action in BooksController (show params hash in log)

    def create
  @book = Book.new params[:book]
  @book.save
  redirect_to "/books"
end

  7. Git Commit

    $ git add .
$ git commit -m "Add books action"

Editing Books

  1. Add an edit link to the books page

    <h1><%= @book.name %></h1>

<%= link_to "Edit", "/books/#{@book.id}/edit" %>

<p>Pages: <%= @book.pages %></p>

  2. Create edit route

    Bookstore::Application.routes.draw do
  get '/books' => 'books#index'
  get '/books/new' => 'books#new'
  get '/books/:id/edit' => 'books#edit'
  get '/books/:id' => 'books#show'
  post '/books' => 'books#create'
end

  3. Create edit action

    def edit
  @book = Book.find params[:id]
end

  4. Create app/views/books/edit.html.erb (copy from new.html.erb)

    <%= form_for @book, url: "/books/#{@book.id}" do |f| %>
  <div>
    <%= f.label :name %>
    <%= f.text_field :name %>
  </div>
  <div>
    <%= f.label :pages %>
    <%= f.text_field :pages %>
  </div>
  <%= f.submit %>
<% end %>

    Need to set url since the book already exists

  5. Add update route

    Bookstore::Application.routes.draw do
  get '/books' => 'books#index'
  get '/books/new' => 'books#new'
  get '/books/:id/edit' => 'books#edit'
  get '/books/:id' => 'books#show'
  post '/books' => 'books#create'
  put '/books/:id' => 'books#update'
end

  6. Add the update action

    def update
  @book = Book.find params[:id]
  @book.update_attributes params[:book]
  redirect_to "/books/#{@book.id}"
end

  7. Git commit

    $ git add .
$ git commit -m "Update books action"

Deleting books

  1. Update app/views/pages/show.html.erb to add

    <%= link_to "Delete", "/books/#{@book.id}", method: :delete %>

  2. Add delete destroy route

    Bookstore::Application.routes.draw do
  get '/books' => 'books#index'
  get '/books/new' => 'books#new'
  get '/books/:id/edit' => 'books#edit'
  get '/books/:id' => 'books#show'
  post '/books' => 'books#create'
  put '/books/:id' => 'books#update'
  delete '/books/:id' => 'books#destroy'
end

  3. Add destroy action

    def destroy
  @book = Book.find(params[:id])
  @book.destroy
  redirect_to "/books"
end

  4. Git commit

    $ git add .
$ git commit -m "Destroy books action"

Cleaning Up

Resource Routes

config/routes.rb can be changed to

Bookstore::Application.routes.draw do
  resources :books
end

Path Helpers

$ rake routes

    books GET    /books(.:format)          books#index
          POST   /books(.:format)          books#create
 new_book GET    /books/new(.:format)      books#new
edit_book GET    /books/:id/edit(.:format) books#edit
     book GET    /books/:id(.:format)      books#show
          PUT    /books/:id(.:format)      books#update
          DELETE /books/:id(.:format)      books#destroy

First column is the name of the path helper. Can be accessed like new_book_path or new_book_url.

  • Use path unless you need the absolute url.
  • Path helpers are automatically set up by resources :books

Updates to use path helpers

  1. app/views/books/index.html

    <h1>Books</h1>

<%= link_to "New Book", new_book_path %>

<table>
  <tr>
    <th>Name</th>
    <th>Pages</th>
  </tr>
  <% @books.each do |book| %>
    <tr>
      <td><%= link_to book.name, book_path(book) %></td>
      <td><%= book.pages %></td>
    </tr>
  <% end %>
</table>

  2. app/views/books/show.html.erb

    <h1><%= @book.name %></h1>

<%= link_to "Edit", edit_book_path(@book) %>
<%= link_to "Delete", book_path(@book), method: :delete %>

<p>Pages: <%= @book.pages %></p>

<!-- New link -->
<%= link_to "Back to all books", books_path %>

  3. app/views/books/edit.html.erb

    <%= form_for @book do |f| %>
  <div>
    <%= f.label :name %>
    <%= f.text_field :name %>
  </div>
  <div>
    <%= f.label :pages %>
    <%= f.text_field :pages %>
  </div>
  <%= f.submit "Edit Book" %>
<% end %>

  4. app/controllers/books_controller.rb

    class BooksController < ApplicationController
  def index
    @books = Book.all
  end

  def show
    @book = Book.find params[:id]
  end

  def new
    @book = Book.new
  end

  def create
    @book = Book.new params[:book]
    @book.save
    redirect_to books_path # Changed line
  end

  def edit
    @book = Book.find params[:id]
  end

  def update
    @book = Book.find params[:id]
    @book.update_attributes params[:book]
    redirect_to book_path(@book) # Changed line
  end

  def destroy
    @book = Book.find params[:id]
    @book.destroy
    redirect_to books_path # Changed line
  end
end

  5. git commit

    $ git add .
$ git commit -m "Books resource route and path helpers"

Extracting a form partial

  1. Show duplication between app/views/books/new.html.erb and app/views/books/edit.html.erb

  2. Create app/views/books/_form.html.erb

    <%= form_for @book do |f| %>
  <div>
    <%= f.label :name %>
    <%= f.text_field :name %>
  </div>
  <div>
    <%= f.label :pages %>
    <%= f.text_field :pages %>
  </div>
  <%= f.submit %>
<% end %>

  3. Update app/views/books/new.html.erb and app/views/books/edit.html.erb

    <%= render partial: "form" %>

  4. Git commit

    $ git add .
$ git commit -m "Extract book form partial"