1. Bruce Scharlau, University of Aberdeen, 2017
Advanced Web Application Development Ruby on Rails – A walk through an app
Bruce Scharlau, University of Aberdeen, 2017

2. What do we know about Rails?
Discuss with your neighbour what you like about Rails
Bruce Scharlau, University of Aberdeen, 2017

3. Bruce Scharlau, University of Aberdeen, 2017
About This Lecture
Form
~40 minutes lectures
Question time
Learning Material
The Hartl Book
Agile Web Development with Rails Chapters 1~6
Bruce Scharlau, University of Aberdeen, 2017

4. Bruce Scharlau, University of Aberdeen, 2017
What is Rails
Ruby on Rails (or Rails, RoR)
open source Ruby framework
developing database-backed web applications
Rail's guiding principles:
less software
faster development
easier to understand, maintain, and enhance
convention over configuration
Less software means you write fewer lines of code to implement your application. Keeping your code small means faster development and fewer bugs, which makes your code easier to understand, maintain, and enhance. Very shortly, you will see how Rails cuts your code burden.
Convention over configuration means an end to verbose XML configuration files--there aren't any in Rails! Instead of configuration files, a Rails application uses a few simple programming conventions that allow it to figure out everything through reflection and discovery. Your application code and your running database already contain everything that Rails needs to know!
Bruce Scharlau, University of Aberdeen, 2017

5. There are many benefits to Rails
Best Technologies
MVC: Model View Controller
Convention over Configuration
DRY: Don’t Repeat Yourself
REST: Representational State Transfer
TDD: Test Driven Development
Continuous and Active Development
Version 1.0 in 2005 (We started teaching it in 2006)
Helpful Online Communities
Bruce Scharlau, University of Aberdeen, 2017

6. Bruce Scharlau, University of Aberdeen, 2017
First Touch with Rails
Create a new application
Rails new story
Generate a controller (and its view)
Rails generate controller story index
app/controllers/story_controller.rb
app/view/story/index.html.erb
Bruce Scharlau, University of Aberdeen, 2017

7. Rails ‘new’ command creates app
rails new cookbook
generates a complete directory tree of folders and files for an empty Rails application
Create models of the objects in the database, and
Controllers which determine what happens in the application
Bruce Scharlau, University of Aberdeen, 2017

8. Creates standard directory structure
controllers subdirectory
where Rails looks to find controller classes
views subdirectory
holds the display templates to fill in with data
models subdirectory
holds the classes that model and wrap the data
helpers subdirectory
holds any helper classes used to assist the model, view, and controller classes
Create models of the objects in the database, and
Controllers which determine what happens in the application
Bruce Scharlau, University of Aberdeen, 2017

9. Start the built in web server
rails server
Each application has built-in development server for using in the app that sits under app/script/server just call it with ‘ruby script/server’ and it starts up on port 3000
Bruce Scharlau, University of Aberdeen, 2017

10. Bruce Scharlau, University of Aberdeen, 2017
MVC is a design pattern
Model
represents the data in the program and business logic
View (templates)
manages the visual display of the data (Presentation Logic)
Controller
provides the means for user interaction with the data (application logic)
Model
View
Controller
Bruce Scharlau, University of Aberdeen, 2017

11. Bruce Scharlau, University of Aberdeen, 2017
MVC eases development
Scalability (the ability for an application to grow)
separate the database from other components
Easier maintenance
components have a low dependency on each other
Reuse
a model may be reused by multiple views, and vice versa
Model
View
Controller
Bruce Scharlau, University of Aberdeen, 2017

12. A Rails request uses MVC
Browser
Model
Controller
View
The browser sends a request for a page to the controller on the server.
The controller retrieves the data it needs from the model in order to respond to the request.
The controller renders the data and sends it to the view.
The view sends the page back to the client for the browser to display.
Bruce Scharlau, University of Aberdeen, 2017

13. Add controllers for the logic
rails generate controller story index
Provides a class to direct requests and responses
Convention: The folder that stores the template is named after the controller
File Generated:
app/controllers/story_controller.rb
app/view/story/index.html.erb
Bruce Scharlau, University of Aberdeen, 2017

14. We could put everything in the story/index view
<blockquote>In a(n) <%=Faker::Hipster.word %> <%= Faker::Job.field %> a young <%= Faker::Hobbit.character %> stumbles across a(n) <%= Faker::Lovecraft.tome %> which spurs him into conflict with <%= Faker::StarTrek.villain %> and her <%= Faker::Hacker.noun %> culminating in <%= Faker::Pokemon.move %> where someone shouts '<%= Faker::Simpsons.quote %>' .</blockquote>
Bruce Scharlau, University of Aberdeen, 2017

15. This works but has issues
What problems are there if we do everything in the view?
Bruce Scharlau, University of Aberdeen, 2017

16. Keep domain logic out of views
The view is there to support the presentation of the model. Any Ruby code should be in the model, a helper, or in the controller.
Bruce Scharlau, University of Aberdeen, 2017

17. StoryController has index method
Request:
StoryController is a class
index is a method, or an action, which variable
Convention: An html template (view) has a one-to-one mapping to the method of a controller
Bruce Scharlau, University of Aberdeen, 2017

18. Story ‘index’ View is simple
app/views/say/index.html.erb:
<h1>Tell me a story...</h1>
<p>Refresh the page for a new story</p>
%></blockquote>
Bruce Scharlau, University of Aberdeen, 2017

19. Understand index.html.erb
<h1>Tell me a story...</h1>
<p>Refresh the page for a new story</p>
<blockquote>
%>
</blockquote>
Convention: html.erb is the extension of standard HTML template that allows ERB tags
<%=…%>: this ERB tag pair is for displaying the output of the Ruby
Bruce Scharlau, University of Aberdeen, 2017

20. The other story/index syntax
<blockquote>In a(n) <%=Faker::Hipster.word %> <%= Faker::Job.field %> a young <%= Faker::Hobbit.character %> stumbles across a(n) <%= Faker::Lovecraft.tome %> which spurs him into conflict with <%= Faker::StarTrek.villain %> and her <%= Faker::Hacker.noun %> culminating in <%= Faker::Pokemon.move %> where someone shouts '<%= Faker::Simpsons.quote %>' .</blockquote>
The <%= somevalue %> syntax lets us display the value in the view
The alternative #{Faker::Pokemon.move} is for when you want the value inside a string
Bruce Scharlau, University of Aberdeen, 2017

21. The story is displayed very simply
Request:
Bruce Scharlau, University of Aberdeen, 2017

22. Why is it better to generate the story in the controller?
Discuss with the person next to you why it’s better to generate the story in the controller
Bruce Scharlau, University of Aberdeen, 2017

23. Routes handles the URL matching
User request
In config/routes.rb
get "story/index” shorthand for the following code:
match ‘story/index’ => ‘story#index’ via => :get
More details about Rails routing
Try “rake routes” in the command line to see all routing information for an application
Bruce Scharlau, University of Aberdeen, 2017

24. What about controllers with models?
Discuss with the person next to you what controllers might do that work with models and views. What will the controller do automatically for you?
Bruce Scharlau, University of Aberdeen, 2017

25. Controllers for models are configured automatically
Generate REST methods for you
Private for ’create’
Bruce Scharlau, University of Aberdeen, 2017

26. Model generation is easy
rails generate model Recipe name:string string
Generate the following two files:
db/migrate/2017xxxxx_create_recipes.rb
app/models/recipe.rb
Run the database migration by
rake db:migrate
Bruce Scharlau, University of Aberdeen, 2017

27. Views are generated for models
Show.html.erb displays a single recipe
Bruce Scharlau, University of Aberdeen, 2017

28. Views are generated for models
_form.html.erb is for ‘new’ and ‘edit’ recipe files
For loop gathers each attribute value of model
Bruce Scharlau, University of Aberdeen, 2017

29. Views are generated for models
index.html.erb is all recipe items
For loop goes through each item in array
Bruce Scharlau, University of Aberdeen, 2017

30. Databases use Migration
rake db:migrate
Rake is Ruby make, a make-like language written in Ruby for performing tasks
Rails comes with built-in support for SQLite3
SQLite3 is a lightweight serverless database application for development
Rails can support other database system too
Bruce Scharlau, University of Aberdeen, 2017

31. Database Configurations
config/database.yml
YML: lightweight format
used in Rails for configuration
development:
adapter: sqlite3
database: db/development.sqlite3 timeout: 5000
test:
database: db/test.sqlite3
timeout: 5000
production:
database: db/production.sqlite3 timeout: 5000
If you use sqlite3, you don’t need to do anything, everything is already configured.
Bruce Scharlau, University of Aberdeen, 2017

32. The Model file can be basic
class Recipe < ApplicationRecord
end
In a controller, you can use:
Recipe.all retrieve all recipies
Recipe.find_by_name(XXXX) retrieve a recipe whose name is XXXX
Bruce Scharlau, University of Aberdeen, 2017

33. Scaffolding generates MVC
rails generate scaffold recipe title:string description:string date:date instructions:text
Bruce Scharlau, University of Aberdeen, 2017

34. Explore Views built-in helpers
<%= text_area_tag(:message, "Hi, nice site", size: "24x6") %>
<%= password_field_tag(:password) %>
<%= hidden_field_tag(:parent_id, "5") %>
<%= search_field(:user, :name) %>
<%= telephone_field(:user, :phone) %>
<%= date_field(:user, :born_on) %>
<%= datetime_local_field(:user, :graduation_day) %>
<%= month_field(:user, :birthday_month) %>
<%= week_field(:user, :birthday_week) %>
<%= url_field(:user, :homepage) %>
<%= _field(:user, :address) %>
<%= color_field(:user, :favorite_color) %>
<%= time_field(:task, :started_at) %>
<%= number_field(:product, :price, in: , step: 0.5) %>
<%= range_field(:product, :discount, in: ) %>
Bruce Scharlau, University of Aberdeen, 2017

35. Form_for binds form to object
Bruce Scharlau, University of Aberdeen, 2017

36. Use ‘form_tag’ for regular forms
This is not tied to a model, so can gather data as required.
Bruce Scharlau, University of Aberdeen, 2017

37. Parameters are passed as array
Bruce Scharlau, University of Aberdeen, 2017

38. Use drop-down lists, etc as needed
We covered these in early practical sessions
Collection_select
Collection_radio_buttons
Bruce Scharlau, University of Aberdeen, 2017

39. Rails API pages offer options
Use API to find more options and details about how to use views
Bruce Scharlau, University of Aberdeen, 2017

40. Layouts are to be rendered
You can render the expected view by default. You can also change the rendered view. Instead of ‘show’ you could use ‘edit’ or something else as required.
Bruce Scharlau, University of Aberdeen, 2017

41. Render only headers if required
Pick option as needed to display result
Bruce Scharlau, University of Aberdeen, 2017

42. Render format as needed
You don’t have to return HTML. render render render html: "<strong>Not Found</strong>".html_safe render plain: “ok” render body: “raw”
When and why would you use these?
Bruce Scharlau, University of Aberdeen, 2017

43. Bruce Scharlau, University of Aberdeen, 2017
Summary
Ruby on Rails offers quick development of data driven web applications
Rails is based on MVC design pattern
Bruce Scharlau, University of Aberdeen, 2017