Rails Quick Start Guide | Blog

About

This app follows the quickstart guide from
http://guides.rubyonrails.org/getting_started.html

Key Rails Commands

rails new -h - see all command line options for rails application rails routes - display defined routes in application rails generate controller ControllerName controller_action - generate controller
rails generate model ModelName attribute:type - generate model
rails db:migrate - run the migration locally rails db:migrate RAILS_ENV=production - run the migration in production

Key Rails Methods & Helpers

form_for - form builder for templates in views. See example in app/views/articles/new.html.erb.
link_to - creates a hyperlink based on text to display and where to go. See example in app/views/welcome/index.html.erb
pluralize - a rails helper that takes a number and a string as its arguments. If the number is greater than one, the string will be automatically pluralized.

Key Concepts/Definitions

routes - connects incoming requests to controllers and actions resource - a collection of similar objects (articles, people, animals). Can create, read, update, and destroy items in a resource; CRUD operations. Rails have a reources method is used to declare a standard REST resource. controller - a class that inherit from ApplicationController. Inside this controller class, we define methods that will become actions for this controller. These actions perform CRUD operations.
migrations - Ruby classes that are designed to make it easy to create and modify database tables. Migration filenames include a timestamp to ensure that they are processed in the order that they were created. Located in db/migrate/YYYYMMDDHHMMSS*.rb

Setup

Create the Blog Application

rails new blog

Say 'Hello'

Need to create at least a controller and a view bin/rails generate controller Welcome index
will generate a controller called Welcome with an action called index
Edit the view in app/views/welcome/index.html.erb, replace all code with <h1>Hello, Rails!</h1>
Change the home page in the routes. Open config/routes.rb. Add: root 'welcome#index'

Add Resources (Articles)

Edit config/routes by adding resources :articles (note: plural form in articles).
Generate Articles controller
bin/rails generate controller Articles.
Inside the app/controllers/articles_controller.rb, define a new method

class ArticlesController < ApplicationController
  def new # add this new method
  end
end

Since there is no associated view yet for the articles controller when we visit localhoset/articles/new, we need to manually create it. Make a new html.erb file in app/views/articles/ called new.html.erb. Add this

<h1>New Article</h1>

Form Builder

Use the form_for method from Form Builder in app/views/articles/new.html.erb

<h1>New Article</h1>

<%= form_for :article do |f| %>
  <p>
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </p>

  <p>
    <%= f.label :text %><br>
    <%= f.text_area :text %>
  </p>

  <p>
    <%= f.submit %>
  </p>
<% end %>

The form needs the correct URL to point to. Edit the form_for line to show: <%= form_for :article, url: articles_path do |f| %>
The articles_path helper tells Rails to point the form to the URI Patern associated with the articles prefix; and the form will (by default) send a POST request to that route.

Creating Articles

In order for the submit button in the form to work, we need to create a create action in the ArticlesController. Edit app/controllers/application_controller.rb

class ArticlesController < ApplicationController
  def new
  end

  def create                                # add this create method
    render plain: params[:article].inspect  # add this render params
  end
end

Create the Article model bin/rails generate model Article title:string text:text This generates a model named Article with a title attribute of type string, and a text attribute of type text.
The generated model also created a database migration file inside the db/migrate directory.
Run the database migration: bin/rails db:migrate
In order to save the data to the database, we need to change the ArticlesController create method. We also define a private method to whitelist the article_params for security.

class ArticlesController < ApplicationController
  def new
  end

  def create
    @article = Article.new(article_params)

    @article.save
    redirect_to @article
  end

  private
    def article_params
      params.require(:article).permit(:title, :text)
    end
end

Create a new file: app/views/articles/show.html.erb

<p>
  <strong>Title:</strong>
  <%= @article.title %>
</p>
 
<p>
  <strong>Text:</strong>
  <%= @article.text %>
</p>

Listing All Articles

We need to get a listing of all the articles. To do so, we need to check the routes again. rails routes. Look for articles GET*

       Prefix Verb   URI Pattern                  Controller#Action
welcome_index GET    /welcome/index(.:format)     welcome#index
     articles GET    /articles(.:format)          articles#index
              POST   /articles(.:format)          articles#create
  new_article GET    /articles/new(.:format)      articles#new
 edit_article GET    /articles/:id/edit(.:format) articles#edit
      article GET    /articles/:id(.:format)      articles#show
              PATCH  /articles/:id(.:format)      articles#update
              PUT    /articles/:id(.:format)      articles#update
              DELETE /articles/:id(.:format)      articles#destroy
         root GET    /                            welcome#index

Add the corresponding index action (articles#index) for that route (articles GET) in the ArticlesController. This corresponding action is the def index... see below:

class ArticlesController < ApplicationController
  def index     # add this method for the index action
    @articles = Article.all
  end
 
  def show
    @article = Article.find(params[:id])
  end
 
  def new
  end
  # more code below ...

Add the view for this action in app/views/articles/index.html.erb

Adding Links

Since we can now create, show, and list articles, we can add some links for navigation. Edit app/views/welcome/index.html:

<h1>Hello, Rails!</h1>
<%= link_to 'My Blog', controller: 'articles' %>

Adding Some Validation

Edit app/models/article.rb

class Article < ApplicationRecord
  validates :title, presence: true, length: { minumum: 5 }
end

These changes will ensure that all articles have a title that is at least 5 characters long. Rails can validate a variety of conditions in a model, including the presence or uniqueness of columns, their format, and the existence of associated objects. See Active Record Validations
Update ArticlesController

class ArticlesController < ApplicationController
  def index
    @articles = Article.all
  end
  def show
    @article = Article.find(params[:id])
  end

  def new
    @article = Article.new
  end

  def create
    @article = Article.new(article_params)

    if @article.save
      redirect_to @article
    else
      render 'new'
    end
  end

  private
    def article_params
      params.require(:article).permit(:title, :text)
    end
end

Make sure the user cannot submit an article without a title. Modify app/views/articles/new.html.erb

Updating Articles

Add an edit action to the ArticlesController. This is generally placed between the new and create actions.

def new
    @article = Article.new
  end

  def edit                                  # add the edit action
    @article = Article.find(params[:id])
  end

  def create
    @article = Article.new(article_params)

    if @article.save
      redirect_to @article
    else
      render 'new'
    end
  end

Create app/views/articles/edit.html.erb

<h1>Editing Article</h1>

<%= form_for :article, url: article_path(@article), method: :patch do |f| %>

  <% if @article.errors.any? %>
    <div id="error_explanation">
      <h2>
        <%= pluralize(@article.errors.count, "error") %>
        prohibited this article from being saved:
      </h2>
      <ul>
        <% @article.errors.full_messages.each do |msg| %>
          <li><%= msg %></li>
        <% end %>
      </ul>
    </div>
  <% end %>

<p>
  <%= f.label :title %><br>
  <%= f.text_field :title %>
</p>

<p>
  <%= f.label :text %><br>
  <%= f.text_area :text %>
</p>

<p>
  <%= f.submit %>
</p>

<% end %>

<%= link_to 'Back', articles_path %>

The method: :patch option tells Rails that we want this form to be submitted via the PATCH HTTP method which is used to update resources according to the REST protocol.
Create an update action in app/controllers/articles_controller.rb. Add it between the create action and private method
Show a link to the edit action in the list of all the articles. Add it to app/views/articles/index.html
Add the edit action to the app/views/articles/show.html.erb as well...

Using Partials to clean up duplication in views

make a new file app/views/articles/_form.html.erb
edit the following files: new.html.erb, edit.html.erb and use the render form` helper.
Add the destroy action in the articles_controller
Add the Destroy link to app/views/articles/index.html.erb

Adding a Second Model

Generate the second model, the comments: rails generate model Comment commenter:string body:text article:references
run the migrations: rails db:migrate

Associating Models

Edit app/models/article.rb to contain 'has_many :comments'
Add a route for Comments in config/routes.rb

resources :articles do
  resources :comments
end

durech11/rails_quickstart_blog