1. Ruby on Rails
B. Meyer, P. Tokarev
Web Technologies – Ruby on Rails – WS 2010/111
The slides are licensed under a
Creative Commons Attribution 3.0 License

2. Content
1. Introduction
2. Main Concepts
1. MVC
2. Convention over Configuration
3. Generation of code
3. Movie Review Demo
4. Additional Features
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3. What is Ruby?
Open‐source Programming Language
Platform independent
Object‐Oriented
Supports multiple paradigms e.g.
Functional Programming
Duck‐Typing
Metaprogramming
First Version (0.95) made public in Dec 1995
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4. Some Ruby Paradigms: Objects
In Ruby everything is an object
Allows simple loops
For‐loop:
generates
Foreach‐loop:
generates
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Hello World
Hello World
2.times{puts “Hello World“}
array = [1, ‘hi‘, 3.14]
array.each {|item| puts item }
1
‘hi‘
3.14

5. Some Ruby Paradigms: Duck‐Typing
Duck‐Typing allows usage of class‐members only by knowing
their name
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class Duck
def description
“A grey duck”
end
def makeNoise
“Quaak!“
end
end
class Cow
def description
“A big cow”
end
def makeNoise
“Moo!“
end
end
def animalSound animal
puts animal.description + “ makes “ + animal.makeNoise
end
“animalSound Duck.new” generates “A grey duck makes Quaak!”
“animalSound Cow.new” generates “A big cow makes Moo!”

6. Some Ruby Paradigms: Metaprogramming
Metaprogramming allows code to write other code at
runtime
Some possibilities:
Redefine classes and methods
Dynamically creating classes
Automatic object serialization
Modifying method calls
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7. What is Ruby on Rails?
Open‐source Web Application
Framework written in Ruby
It was published by
David Heinemeyer Hanson
Rails was invented for an
Application named „Basecamp“
Rails was first presented in 2004
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8. History
Version 1 was published on December 13th 2005
Version 2.0 was published on March 15th 2009
Had more than a hundred improvements e.g.:
XML deserialization
Debugger
Performance improvements
Version 3.0 was published on August 29th 2010
Merges merb with Rails → one big Ruby‐based Framework
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9. Principles
Ruby on Rails uses two main priciples:
Convention over Configuration
→ Easy to set up
Don‘t repeat yourself (DRY)
→ Rapid development
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Image:

10. Content
1. Introduction
2. Main Concepts
1. MVC
2. Convention over Configuration
3. Generation of code
3. Movie Review Demo
4. Additional Features
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11. MVC inside Rails
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Controller
View
Model
Client
Server
Dispatcher
ActionController
ActionView ActiveRecord
DBMS
request
forward
request
load
request
respond
redirect
render
querydata
display

12. Convention over Configuration
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Model
movie
Controller
movies_controller
show edit
Table in DB
movies
new
Model
Controller
View

13. Generation of code
Rails command: rails generate scaffold movie
Table in database
Folder and file structure for model, view and
controller
Creates all 'CRUD' actions for controller
Creates all 'CRUD' views
1 line of code generates more then 100 lines of code
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14. Content
1. Introduction
2. Main Concepts
1. MVC
2. Convention over Configuration
3. Generation of code
3. Movie Review Demo
4. Additional Features
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15. Movie Review Demo
Create Project
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16. Movie Review Demo
Create Project
Use scaffolding
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17. Movie Review Demo
Create Project
Use scaffolding
Add new attributes to models
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18. Movie Review Demo
Create Project
Use scaffolding
Add new attributes to models
Add new model
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19. Movie Review Demo
Create Project
Use scaffolding
Add new attributes to models
Add new model
Create one to many relation
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Movie
id :int
title :string
...
Comment
id :int
text :text
movie_id :int

20. Content
1. Introduction
2. Main Concepts
1. MVC
2. Convention over Configuration
3. Generation of code
3. Movie Review Demo
4. Additional Features
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21. More features
Session management
Available for different languages (e.g. Java)
Various DB support
MySQL, Postgres, Oracle etc.
Partials
Code that belongs to several documents DRY
Tests
Rails creates test files automatically
Layouts
Customize look and feel
Plug‐ins
Open‐source many Plug‐ins are available
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22. Implemented in Rails
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23. Summary
Rails is written in Ruby
Ruby != Rails
Open‐source
Web application framework
Convention over Configuration
Model‐View‐Controller (MVC)
Don’t repeat yourself (DRY)
Additional features available
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