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Learning Ruby with
RubyWarrior
Mr. Big Cat
2011/1/25

About Me
�� ؈
�� I like coding
�� ؈��͇�� http://gaagaaga.blogspot.com
�� Twitter&Plurk: miaout17

Outline
�� Introducing RubyWarrior
�� Playing RubyWarrior
�� Solving RubyWarrior with Metaprogramming
and DSL

What is RubyWarrior?
A game designed to teach the Ruby language
and artificial intelligence in a fun, interactive way.

Who created RubyWarrior?

RubyWarrior is created
by Ryan Bates, the
author of Railscasts.

How to start?
In your shell:

$ gem install rubywarrior
$ rubywarrior

Demo!

How to play?

Read README and
Edit Your Script
Edit Your Script

Run RubyWarrior

No
Level Passed?

Yes
Jump to the next level
Gain New Abilities Demo!

What's Within?

Player RubyWarrior::Turn

play_turn attack!
... detonate!
rescue!
rest!
shoot!
walk!
RubyWarrior::Space
direction_of
wall? distance_of
enemy? health
captive?
empty? feel
stairs? listen
ticking? look

Epic Mode

Beginner Intermediate

Level 1 Level 1
Level 2 Level 2
Epic Epic
Mode Level 3 Level 3 Mode
Level 4 Level 4
Level 5 Level 5
Level 6 Level 6
Level 7 Level 7
Level 8 Level 8
Level 9 Level 9

Demo!

My Epic Mode Solution
�� An AI logic that pass intermediate epic mode
with all-S rank
�� Three implementation styles:
�� Naive Solution
�� Pure-OO Solution
�� Metaprogramming&DSL Solution

Naive Solution
DIRS.each do |dir|
if @warrior.feel(dir).ticking?
@warrior.rescue!(dir)
return
end
end

return if walk_to_ticking!

DIRS.each do |dir|
if should_detonate?(dir)
detonate!(dir)
return
end
end

DIRS.each do |dir|
if @warrior.feel(dir).enemy?
@warrior.attack!(dir)
return
end
end

DIRS.each do |dir|
if @warrior.feel(dir).captive?
return
end
end

walk!(direction_of_stairs)

Demo!

Pure OO Solution

Demo!

Metaprogramming&DSL Solution
�� Today we won't focus on how to do
metaprogramming and create a DSL
�� We focus on how metaprogramming & DSL
make our life easier

What's Metaprogramming?

"Writing a program that writes programs."

What's Metaprogramming?

"Writing a program that writes programs."
��ֹ��С��

We use attr_accessor everyday
class Warrior
attr_accessor :health
end

w = Warrior.new
w.health = 95
puts w.health

What is attr_accessor?
class Warrior class Warrior
attr_accessor :health def health
end @health
end
w = Warrior.new def health=(val)
w.health = 95 @health = val
puts w.health end
end

w = Warrior.new
w.health = 59
puts w.health

attr_acccessor is a METHOD!

Getter/Setter in Java
class Warrior
{
public void setHealth(int val)
{
health = val;
}
public int getHealth()
{
return health;
}
private int health;
}

public class AttrAccessor
{
public static void main(String[] args)
{
Warrior s = new Warrior();
s.setHealth(95);
System.out.println("Health = " + s.getHealth());
}
}

Delegation
class Player

def hurt?
return false unless @last_health
return @warrior.health < @last_health
end

def play_turn(warrior)
@warrior = warrior
if @warrior.feel.captive?
@warrior.rescue!
elsif !@warrior.feel.empty?
@warrior.attack!
elsif @warrior.health == 20 || hurt?
@warrior.walk!
else
@warrior.rest!
end
@last_health = @warrior.health
end

end

Delegation
class Player class Player

def hurt? def hurt?
return false unless @last_health return false unless @last_health
return @warrior.health < @last_health return health < @last_health
end end

def play_turn(warrior) def play_turn(warrior)
@warrior = warrior @warrior = warrior
if @warrior.feel.captive? if feel.captive?
@warrior.rescue! rescue!
elsif !@warrior.feel.empty? elsif !feel.empty?
@warrior.attack! attack!
elsif @warrior.health == 20 || hurt? elsif health == 20 || hurt?
@warrior.walk! walk!
else else
@warrior.rest! rest!
end end
@last_health = @warrior.health @last_health = health
end end

end end

Delegation Implementation
class Player

def health
@warrior.health
end

def feel
@warrior.feel
end

def rescue!
@warrior.rescue!
end

def attack!
@warrior.attack!
end

def walk!
@warrior.walk!
end

def rest!
@warrior.rest!
end

Delegation Implementation
class Player require 'forwardable'

def health class Player
@warrior.health
end
extend Forwardable
def feel
@warrior.feel def_delegators :@warrior, :health, :feel,
end :rescue!, :attack!, :walk!, :rest!

def rescue!
@warrior.rescue!
end

def attack!
@warrior.attack!
end

def walk!
@warrior.walk!
end

def rest!
@warrior.rest!
end

Domain Specific Language(DSL)
solution
DIRS.each do |dir| require 'player_helper'
if @warrior.feel(dir).ticking?
return class Player
end
end
include PlayerHelper
return if walk_to_ticking!

DIRS.each do |dir| def_strategries do
if should_detonate?(dir) directional(:rescue!, :ticking?)
detonate!(dir)
strategy { rest! if rest_when_ticking? }
return
end directional(:detonate!, :should_detonate?)
end directional(:attack!, :enemy?)
DIRS.each do |dir|
directional(:rescue!, :captive?)
if @warrior.feel(dir).enemy? strategy { walk!(direction_of_stairs) }
@warrior.attack!(dir) end
return
end
end

DIRS.each do |dir|
if @warrior.feel(dir).captive? Player
return
end
end
PlayerHelper
walk!(direction_of_stairs)

Demo!

DSL is Everywhere
�� Rails Routing

resources :forums, :only => [:index, :show] do
resources :posts
end

namespace :admin do
resources :forums do
resources :posts, :except => [:new, :create]
end
end

DSL is Everywhere
�� Rake Task

task :drink do
puts "I drink juice"
end

task :eat do
puts "I eat sandwich"
end

task :breakfast => [:drink, :eat] do
puts "I ate breakfast"
end

Conclusion:
The Ruby way I know

My RubyWarrior
Rails Rake
Script
Implementing high-
level logic is incredible
Player Rails App Rake Task simple with easy-to-
use API and DSL

Rails
Write API and create
ActiveRecord ActionMailer DSL with
PlayerHelper Rake metaprogramming
ActionPack ActiveSupport techniques

...

Lecture martial
�� Source code is available on github
https://github.com/gaagaaga/warrior-tuesday
�� i-naive
�� i-oo
�� i-dsl
�� dsl-starter
�� ݺ�ߣ will be on slideshare (coming soon)

Learning Resource
�� For Beginners:
�� TryRuby: http://tryruby.org/
�� RubyWarrior: https://github.com/ryanb/ruby-warrior
�� The Ruby Programming Language (Book)
�� For Intermediate:
�� Eloquent Ruby (Book)
�� Metaprogramming Ruby (Book)

�ݺ�ߣ

Learning Ruby with RubyWarrior

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