Building a Rails Application

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Emery Anderson
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1 Building a Rails Application

3 Let s get started! Use MySQL to create a depot_development database Create a new Ruby on Rails project called depot Make sure root password is included in Configuration/database.yml

4 Generate the product model Note the files that are generated. We are particularly interested in: product.rb the model 001_create_products.rb the database migration

5 001_create_products.rb Modify this file, and then apply the migration: class CreateProducts < ActiveRecord::Migration def self.up create_table :products do t t.column :title, :string t.column :description, :text end end t.column :image_url, def self.down drop_table :products end end :string

6 Got a Model, now how about a Controller? Generate a Controller called admin (leave Views blank for now) Add the following line into the class AdminController: scaffold :product Now Run the project! Point the browser to: localhost:3000/admin

7 Add a missing column Generate and apply a migration named add_price: class AddPrice < ActiveRecord::Migration end def self.up add_column :products, :price, :decimal, :precision => 8, :scale => 2, :default => 0 end def self.down remove_column :products, :price end

8 Validation! Refresh the browser to see the Price column But notice you can type anything you like (or nothing at all!) in the New Product form

9 product.rb class Product < ActiveRecord::Base end validates_presence_of :title, :description, :image_url

11 product.rb class Product < ActiveRecord::Base validates_presence_of :title, :description, :image_url validates_numericality_of :price end

13 more validation class Product < ActiveRecord::Base validates_presence_of :title, :description, :image_url validates_numericality_of :price validates_uniqueness_of :title validates_format_of :image_url, :with => %r{\.(gif jpg png)$}i, :message => "must be a URL for a GIF, JPG or PNG image" protected def validate errors.add(:price, "should be at least 0.01") if price.nil? price < 0.01 end end

14 Explanation of the Regular Expression Constructor is: %r{ pattern }options %r{\.} Escape the full stop so it is matched as a full stop, not interpreted ( any character ) %r{\.(gif jpg png)} Follow the full stop by gif, jpg or png %r{\.(gif jpg png)$} Match the pattern at the end of the line %r{\.(gif jpg png)$}i And make it case insensitive

16 Prettier Listings The List of Products in the Admin view looks pretty poor. We will now explicitly generate the Scoffold and then customise it.

17 generate scaffold for model: product and controller: admin select overwrite existing files

18 exists app/controllers/ exists app/helpers/ exists app/views/admin exists app/views/layouts/ exists test/functional/ dependency model exists app/models/ exists test/unit/ exists test/fixtures/ skip app/models/product.rb identical test/unit/product_test.rb identical test/fixtures/products.yml create app/views/admin/_form.rhtml create app/views/admin/list.rhtml create app/views/admin/show.rhtml create app/views/admin/new.rhtml create app/views/admin/edit.rhtml create app/controllers/admin_controller.rb create test/functional/admin_controller_test.rb identical app/helpers/admin_helper.rb create app/views/layouts/admin.rhtml create public/stylesheets/scaffold.css

19 app/views/admin/list.rhtml <h1>listing products</h1> <table> <tr> <% for column in Product.content_columns %> <th><%= column.human_name %></th> <% end %> </tr> <% for product %> <tr> <% for column in Product.content_columns %> <td><%=h product.send(column.name) %></td> <% end %> <td><%= link_to 'Show', :action => 'show', :id => product %></td> <td><%= link_to 'Edit', :action => 'edit', :id => product %></td> <td><%= link_to 'Destroy', { :action => 'destroy', :id => product }, :confirm => 'Are you sure?', :method => :post %></td> </tr> <% end %> </table> <%= link_to 'Previous page', { :page } %> <%= link_to 'Next page', { :page } %> <br /> <%= link_to 'New product', :action => 'new' %>

20 Let s have some test data generate migration: add_test_data paste in the data from the web (Also copy images and depot.css) run the migration

21 First, link in a prettier stylesheet: depot.css Modify views/layouts/admin.rhtml <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" " <html xmlns=" xml:lang="en" lang="en"> <head> <meta http-equiv="content-type" content="text/html;charset=utf-8" /> <title>admin: <%= controller.action_name %></title> <%= stylesheet_link_tag 'scaffold', 'depot' %> </head> <body> <p style="color: green"><%= flash[:notice] %></p> <%= yield %> </body> </html>

22 Second, replace the dynamic column display Replace Views/admin/list.rhtml Will provide the file, which has a simple table-based layout Refresh the browser and it should like much tidier - hopefully!

23 <% for product %> <tr valign="top" class="<%= cycle('list-line-odd', 'list-line-even') %>"> <td> <img class="list-image" src="<%= product.image_url %>"/> </td> <td width="60%"> <span class="list-title"><%= h(product.title) %></span><br /> <%= h(truncate(product.description, 80)) %> </td>

25 Creating the Catalogue Display Generate a Controller called store With a View called index Now point the browser to: localhost:3000/store

27 store_controller.rb class StoreController < ApplicationController def = Product.find_products_for_sale end end

28 product.rb class Product < ActiveRecord::Base def self.find_products_for_sale find(:all, :order => "title") end # Validation stuff... validates_presence_of :title, :description, :image_url... end

29 index.rhtml <h1>your pragmatic catalogue</h1> <% for product -%> <div class="entry"> <%= image_tag(product.image_url) %> <h3><%= h(product.title) %></h3> <%= product.description %> <span class="price"><%= product.price %> </span> </div> <% end %>

appendix B: Working with Ruby on Rails

appendix B: Working with Ruby on Rails B1 appix B: Working with Ruby on Rails APPENDIX B B2 Since the beginning of the Web, both static and dynamic typed languages have been used for writing web applications. Java and its cousin C# have emerged