Design Pattern
-- from Java to Ruby
Richard
Ekohe
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Web Development & Graphic Design
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Why use Design Pattern
 For reuse
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Why use Design Pattern
 For communication
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Web Development & Graphic Design
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Why use Design Pattern
Define a Node interface, all of leaf nodes and
internal nodes should implements the
interface, internal nodes has a list that
 For communication includes other internal nodes and leaf nodes
and it can add and remove sub-nodes. But
leaf node can’t have add sub-node method.
www.ekohe.com
Web Development & Graphic Design
China Ruby on Rails Development - Rails Consulting - Rails Services - Merb - Offshore Web Development

Why use Design Pattern
Define a Node interface, all of leaf nodes and
internal nodes should implements the
interface, internal nodes has a list that
 For communication includes other internal nodes and leaf nodes
and it can add and remove sub-nodes. But
leaf node can’t have add sub-node method.
www.ekohe.com
Web Development & Graphic Design
China Ruby on Rails Development - Rails Consulting - Rails Services - Merb - Offshore Web Development

Why use Design Pattern
Define a Node interface, all of leaf nodes and
internal nodes should implements the
interface, internal nodes has a list that
 For communication includes other internal nodes and leaf nodes
and it can add and remove sub-nodes. But
leaf node can’t have add sub-node method.
www.ekohe.com
Web Development & Graphic Design
China Ruby on Rails Development - Rails Consulting - Rails Services - Merb - Offshore Web Development

Why use Design Pattern
 For communication
www.ekohe.com
Web Development & Graphic Design
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Why use Design Pattern
 For communication
Composite
Pattern
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Why use Design Pattern
 For communication
Composite
Pattern
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Difference from java to ruby
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Difference from java to ruby
 Classes are Objects
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Difference from java to ruby
 Classes are Objects
 Messages, not function call
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Difference from java to ruby
 Classes are Objects
 Messages, not function call
 Duck Typing
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Difference from java to ruby
 Classes are Objects
 Messages, not function call
 Duck Typing
 Mixin
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Singleton Pattern
 ensures a class has only one instance, and
provides a global point of access to it
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Singleton Pattern
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Singleton Pattern
You are my
only wife
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Singleton Pattern
You are my
You are my
only husband
only wife
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Singleton Pattern -- java
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Singleton Pattern -- java
 Eager loading
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Singleton Pattern -- java
 Eager loading
 Lazy loading
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Singleton Pattern -- ruby
 Ruby built-in singleton
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Singleton Pattern -- ruby
 Ruby built-in singleton
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www.ekohe.com
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www.ekohe.com
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www.ekohe.com
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www.ekohe.com
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Ruby for Design Pattern
 Built-in (Singleton)
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Observer Pattern
 defines a one-to-many dependency between
objects so that when one object changes state,
all of its dependents are notified and updated
automatically
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Observer Pattern
Subscribe
Temperature
Detector
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Observer Pattern
Subscribe
Temprature
Temperature
changed
Detector
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Observer Pattern
Notify Notify
Subscribe
Temprature
Temperature
changed
Detector
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Observer Pattern -- java
 Define interface by yourself
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Observer Pattern -- java
 Define interface by yourself
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Observer Pattern -- java
 Define interface by yourself
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Observer Pattern -- java
 Define interface by yourself
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Observer Pattern -- java
 Define interface by yourself
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Observer Pattern -- java
 Define interface by yourself
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Observer Pattern -- java
 Java built-in observer
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Observer Pattern -- java
 Java built-in observer
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Observer Pattern -- ruby
 Ruby built-in observer
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Observer Pattern -- ruby
 Ruby built-in observer
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Observer Pattern -- ruby
 Ruby built-in observer
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www.ekohe.com
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www.ekohe.com
Web Development & Graphic Design
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www.ekohe.com
Web Development & Graphic Design
China Ruby on Rails Development - Rails Consulting - Rails Services - Merb - Offshore Web Development

Ruby for Design Pattern
 Built-in (Singleton, Observer)
 Mixin
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Iterator Pattern
 provides a way to access the elements of an
aggregate object sequentially without exposing
its underlying representation
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Iterator Pattern
Count 1 2 3 10
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Iterator Pattern -- java
 Java built-in Iterator and mock Iterator
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Iterator Pattern -- java
 Java built-in Iterator and mock Iterator
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Iterator Pattern -- java
 Java built-in Iterator and mock Iterator
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Iterator Pattern -- java
 Java built-in Iterator and mock Iterator
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Iterator Pattern -- ruby
 Nothing, just .each
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Iterator Pattern -- ruby
 Nothing, just .each
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Iterator Pattern -- ruby
 Nothing, just .each
www.ekohe.com
Web Development & Graphic Design
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Ruby for Design Pattern
 Built-in (Singleton, Observer, Iterator)
 Mixin
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Simple Factory Pattern
 returns an instance of one of several possible
classes, depending on the data provided to it.
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Simple Factory Pattern
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Simple Factory Pattern -- java
 Compare with String, a lot of if/else
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Simple Factory Pattern -- java
 Compare with String, a lot of if/else
www.ekohe.com
Web Development & Graphic Design
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Simple Factory Pattern -- java
 Compare with String, a lot of if/else
www.ekohe.com
Web Development & Graphic Design
China Ruby on Rails Development - Rails Consulting - Rails Services - Merb - Offshore Web Development

Simple Factory Pattern -- java
 Compare with String, a lot of if/else
www.ekohe.com
Web Development & Graphic Design
China Ruby on Rails Development - Rails Consulting - Rails Services - Merb - Offshore Web Development

Simple Factory Pattern -- java
 Compare with String, a lot of if/else
www.ekohe.com
Web Development & Graphic Design
China Ruby on Rails Development - Rails Consulting - Rails Services - Merb - Offshore Web Development

Simple Factory Pattern -- java
 Compare with String, a lot of if/else
www.ekohe.com
Web Development & Graphic Design
China Ruby on Rails Development - Rails Consulting - Rails Services - Merb - Offshore Web Development

Simple Factory Pattern -- ruby
 Classes are Objects
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Web Development & Graphic Design
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Simple Factory Pattern -- ruby
 Classes are Objects
www.ekohe.com
Web Development & Graphic Design
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Simple Factory Pattern -- ruby
 Classes are Objects
www.ekohe.com
Web Development & Graphic Design
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Simple Factory Pattern -- ruby
 Classes are Objects
www.ekohe.com
Web Development & Graphic Design
China Ruby on Rails Development - Rails Consulting - Rails Services - Merb - Offshore Web Development

Ruby for Design Pattern
 Built-in (Singleton, Observer, Iterator)‫‏‬
 Mixin
 Classes are Objects
www.ekohe.com
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Command Pattern
 encapsulates a request as an object, thereby
letting you parameterize clients with different
requests, queue or log requests, and support
undoable operations.
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Command Pattern
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Command Pattern -- java
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Command Pattern -- java
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Command Pattern -- java
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Command Pattern -- java
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Command Pattern -- java
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Command Pattern -- ruby
 Proc
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Command Pattern -- ruby
 Proc
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Ruby for Design Pattern
 Built-in (Singleton, Observer, Iterator)‫‏‬
 Mixin
 Classes are Objects
 Proc
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Other Design Patterns
Make use of ruby advantage
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Ruby's Principle
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Ruby's Principle
 DRY – Don't Repeat Yourself
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Ruby's Principle
 DRY – Don't Repeat Yourself
 Convention Over Configuration
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Resources
 Design Pattern – Elements of Reusable Object-Oriented Software
Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides
 Head First Design Pattern
Kathy Sierra, Bert Bates
 Design Pattern in Ruby
Russ Olsen
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Q&A
happy to discuss and fix my mistakes
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