rails-demo.md

Rails Demo

Install Rails

gem install rails
rails _5.2.3_ new blog -d postgresql --skip-turbolinks --skip-coffee
cd blog
rails db:create

Start the Rails Server

rails server

Routes

Open the file config/routes.rb in your editor.

Rails.application.routes.draw do
  root 'articles#index'
end

To see your work:

rake routes

Create a controller: (controller names are plural)

touch app/controllers/articles_controller.rb

Add a method for each RESTful action.

class ArticlesController < ApplicationController
  def index
  end

  def show
  end

  def new
  end

  def edit
  end

  def create
  end

  def update
  end

  def destroy
  end
end

(view directory names are plural, file names are normally singular)

mkdir app/views/articles
touch app/views/articles/index.html.erb
touch app/views/articles/new.html.erb

Add this code into app/views/articles/index.html.erb

<h1>hello world</h1>

Try it out

Add this code into app/views/articles/new.html.erb

<%= form_with scope: :article, url: articles_path, local: true do |form| %>
  <p>
    <%= form.label :title %><br>
    <%= form.text_field :title %>
  </p>

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

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

Add the route to config/routes.rb

  get '/articles/new' => 'articles#new', as: 'new_article'

Change the create method to output the params being sent to it:

def create
  render plain: params[:article].inspect
end

Add the route to config/routes.rb

  post '/articles' => 'articles#create'

Try it out in the browser:

http://localhost:3000/articles/new

Create the table:

rails generate migration articles

Look inside the generated file:

class Articles < ActiveRecord::Migration
  def change
  end
end

Inside the change method add your table creation code:

create_table :articles do |t|
  t.string :title
  t.text :text
  t.timestamps
end

Run the migration

rails db:migrate

Create the model

touch app/models/article.rb (model filenames are singular)

class Article < ApplicationRecord
  # AR classes are singular and capitalized by convention
end

Start saving things in the controller:

def create
  @article = Article.new(article_params)

  @article.save
  redirect_to @article
end

At the bottom of the file put the private article_params security method:

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

Add to the show controller

def show
  @article = Article.find(params[:id])
end

Create a new file app/views/articles/show.html.erb with the following content:

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

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

Also add a link to go back to the index action as well, so that people who are viewing a single article can go back and view the whole list:

<%= link_to 'Back', root_path %>

Add the route to the config/routes.rb file

  get '/articles/:id' => 'articles#show' , as: 'article'

Add to the index controller

def index
  @articles = Article.all
end

Add the view for this action, located at app/views/articles/index.html.erb

<h1>Listing articles</h1>

<table>
  <tr>
    <th>Title</th>
    <th>Text</th>
    <th></th>
  </tr>

  <% @articles.each do |article| %>
    <tr>
      <td><%= article.title %></td>
      <td><%= article.text %></td>
      <td><%= link_to 'Show', article_path(article) %></td>
    </tr>
  <% end %>
</table>

Add this "New Article" link to app/views/articles/index.html.erb placing it above the tag:

<%= link_to 'New article', new_article_path %>

Add another link in app/views/articles/new.html.erb underneath the form, to go back to the index action:

<%= form_with scope: :article, url: articles_path, local: true do |form| %>
  ...
<% end %>

<%= link_to 'Back', root_path %>

Editing

Add an edit action to the ArticlesController

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

create the route

get '/articles/:id/edit' => 'articles#edit', as: 'edit_article'

Create a file called app/views/articles/edit.html.erb

<h1>Edit article</h1>

<%= form_with scope: :article, model: @article, local: true do |form| %>

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

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

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

<% end %>

<%= link_to 'Back', root_path %>

Add the route to the config/routes.rb file

patch '/articles/:id' => 'articles#update'

Create the update action in app/controllers/articles_controller.rb

def update
  @article = Article.find(params[:id])

  @article.update(article_params)
  redirect_to @article
end

Add the edit link to app/views/articles/index.html.erb to make it appear next to the "Show" link:

<td><%= link_to 'Edit', edit_article_path(article) %></td>

Also add one to the app/views/articles/show.html.erb template as well

<%= link_to 'Edit', edit_article_path(@article) %>

Deleting

Add the route to the config/routes.rb file

delete '/articles/:id' => 'articles#destroy'

Add the delete controller to app/controllers/articles_controller.rb

def destroy
  @article = Article.find(params[:id])
  @article.destroy

  redirect_to root_path
end

Add a 'Destroy' link to your index action template, inside the loop (app/views/articles/index.html.erb)

<td><%= link_to 'Destroy', article_path(article),
        method: :delete,
        data: { confirm: 'Are you sure?' } %></td>

Pairing Exercise

Run the above code.