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Making tastier code through
Refactoring
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Person.new(
name: 'Gabriel Ortuño',
job: 'ASPgems',
web: 'arctarus.com',
pet_project: 'rezets.com',
github: 'arctarus',
twitter: 'arctarus'
)
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1. Introduction
2. Sample
3. Conclusions
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Refactoring?
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"Refactoring is the process of changing a
software system in such a way that it
does not alter the external behavior of
the code yet improves its internal
structure"
Martin Fowler
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No content
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Code Smells
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Refactoring Toolbox
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Why?
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Green Field
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Legacy Code
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When?
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No content
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1. Introduction
2. Sample
3. Conclusions
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New Task
Print nutritional report in HTML
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Recipe
name
ingredients
nutritional_report
Ingredient
amount
food
Food
name
nutritional_code
HIGH
LOW
REGULAR
1:N
1:1
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No content
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class Recipe
...
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}\n"
self.ingredients.each do |ingredient|
this_calories = 0
# add calories by ingredient
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (ingredient.amount - 2) * 1.5 if ingredient.amount > 2
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (ingredient.amount - 3) * 1.5 if ingredient.amount > 3
end
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "\t" + ingredient.food.name + "\t" + this_calories.to_s + "\n"
total_calories += this_calories
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end
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Whyyyy?
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1º Build a solid set of tests
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describe Recipe do
let(:recipe) { Recipe.new("Lentils with chorizo") }
let(:chorizo) { Food.new('chorizo', Food::HIGH) }
let(:lentil) { Food.new('lentil', Food::LOW) }
let(:potatoe) { Food.new('potatoe', Food::REGULAR) }
it "has a name" do
recipe.name.should == "Lentils with chorizo"
end
describe "calories" do
it "without ingredients are 0"
it "with one regular ingredient are 1.5"
it "with one regular ingredient and amount > 3 are 3"
it "with one high ingredient are 5"
end
...
end
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$ rspec spec
..............
Finished in 0.00742 seconds
14 examples, 0 failures
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class Recipe
...
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}\n"
self.ingredients.each do |ingredient|
this_calories = 0
# add calories by ingredient
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (ingredient.amount - 2) * 1.5 if ingredient.amount > 2
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (ingredient.amount - 3) * 1.5 if ingredient.amount > 3
end
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "\t" + ingredient.food.name + "\t" + this_calories.to_s + "\n"
total_calories += this_calories
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end
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Long Method
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Comments
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class Recipe
...
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}\n"
self.ingredients.each do |ingredient|
this_calories = 0
# add calories by ingredient
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (ingredient.amount - 2) * 1.5 if ingredient.amount > 2
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (ingredient.amount - 3) * 1.5 if ingredient.amount > 3
end
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "\t" + ingredient.food.name + "\t" + this_calories.to_s + "\n"
total_calories += this_calories
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end
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...
# add calories by ingredient
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (ingredient.amount - 2) * 1.5 if ...
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (ingredient.amount - 3) * 1.5 if ...
end
...
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Extract Method
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class Recipe
...
def calories_for(ingredient)
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end
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def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}\n"
self.ingredients.each do |ingredient|
this_calories = calories_for(ingredient)
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.
amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "\t" + ingredient.food.name + "\t" + this_calories.to_s +
"\n"
total_calories += this_calories
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{nutritional_points} nutritional points"
result
end
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$ rspec spec
.FFFFFFFFFFFFF
Finished in 0.00742 seconds
14 examples, 13 failures
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No content
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class Recipe
...
def calories_for(ingredient)
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end
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class Recipe
...
def calories_for(ingredient)
this_calories = 0
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end
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$ rspec spec
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Finished in 0.00742 seconds
14 examples, 0 failures
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class Recipe
...
def calories_for(ingredient)
this_calories = 0
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end
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class Recipe
...
def calories_for(ingredient)
this_calories = 0
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end
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Feature Envy
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Move Method
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class Ingredient
...
def calories
this_calories = 0
case food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (amount - 2) * 1.5 if amount > 2
when Food::LOW
this_calories += amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (amount - 3) * 1.5 if amount > 3
end
end
end
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class Recipe
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}\n"
self.ingredients.each do |ingredient|
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.
amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "\t" + ingredient.food.name + "\t"
result += ingredient.calories.to_s + "\n"
total_calories += ingredient.calories
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end
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describe Ingredient do
let(:chorizo) { Food.new('chorizo',Food::HIGH) }
let(:lentil) { Food.new('lentil', Food::LOW) }
let(:potatoe) { Food.new('potatoe', Food::REGULAR) }
describe 'calories' do
it "with one regular food are 1.5"
it "with one regular food and amount > 3 are 3"
it "with one high food are 5"
it "with one high food and amount > 2 are 6.5"
it "with one low food are 3"
end
end
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$ rspec spec
...................
Finished in 0.00588 seconds
19 examples, 0 failures
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class Recipe
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}\n"
self.ingredients.each do |ingredient|
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH &&
ingredient.amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "\t" + ingredient.food.name + "\t"
result += ingredient.calories.to_s + "\n"
total_calories += ingredient.calories
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end
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Remove
Feature Envy
with
Extract Method
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class Ingredient
...
def nutritional_points
if food.nutritional_code == Food::HIGH && amount > 1
2
else
1
end
end
end
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class Recipe
...
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}\n"
self.ingredients.each do |ingredient|
nutritional_points += ingredient.nutritional_points
# show figures for this rental
result += "\t" + ingredient.food.name + "\t"
result += ingredient.calories.to_s + "\n"
total_calories += ingredient.calories
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{nutritional_points} nutritional point
result
end
end
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describe Ingredient do
describe "nutritional points" do
it "is 2 if food is high and amount > 1"
it "is 1 if food is high and amount = 1"
it "is 1 if food is not high and amount = 1"
it "is 1 if food is not high and amount > 1"
end
end
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$ rspec spec
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Finished in 0.00588 seconds
23 examples, 0 failures
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class Recipe
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}\n"
self.ingredients.each do |ingredient|
nutritional_points += ingredient.nutritional_points
# show figures for this rental
result += "\t" + ingredient.food.name + "\t"
result += ingredient.calories.to_s + "\n"
total_calories += ingredient.calories
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{nutritional_points} nutritional point
result
end
end
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Replace Temp with Query
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class Recipe
...
def total_calories
ingredients.sum(:calories)
end
def total_nutritional_points
ingredients.sum(:nutritional_points)
end
end
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class Recipe
def nutritional_report
result = "Nutritional Report for #{name}\n"
ingredients.each do |ingredient|
# show figures for this rental
result += "\t" + ingredient.food.name + "\t"
result += ingredient.calories.to_s + "\n"
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{total_nutritional_points} nutritional
result
end
...
end
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$ rspec spec
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Finished in 0.00621 seconds
23 examples, 0 failures
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class Recipe
def nutritional_report
result = "Nutritional Report for #{name}\n"
ingredients.each do |ingredient|
# show figures for this rental
result += "\t" + ingredient.food.name + "\t"
result += ingredient.calories.to_s + "\n"
end
# add footer lines
result += "Total calories are #{total_calories}\n"
result += "You earned #{total_nutritional_points} nutritional
result
end
...
end
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class Recipe
def html_nutritional_report
result = "
Nutritional Report for #{name}
" ingredients.each do |ingredient| # show figures for this rental result += "#{ingredient.food.name} " result += "{ingredient.calories}
" end # add footer lines result += "Total calories are #{total_calories}
" result += "You earned #{total_nutritional_points} " result += "nutritional points
" result end ... end HTML ReportSlide 57
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More Refactoring?
Replace Method
with Method Objet
Template Method Pattern
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class NutritionalReport
def initialize(recipe)
@recipe = recipe
end
def output
head
body
foot
end
def head
...
def body
...
def line(ingredient)
...
def foot
...
end
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class HTMLNutritionalReport < NutritionalReport
def head
"
Nutritional Report for #{name}
" end def line(ingredient) "#{ingredient.food.name} #{ingredient.calories}
" end def foot result = "Total calories are #{@recipe.total_calories}
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WIN!
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class Ingredient
...
def calories
this_calories = 0
case food.nutritional_code
when Food::HIGH
this_calories += (amount - 2) * 1.5 if amount > 2
this_calories += 5
when Food::LOW
this_calories += amount * 3
when Food::REGULAR
this_calories += (amount - 3) * 1.5 if amount > 3
this_calories += 1.5
end
end
def nutritional_points
(food.nutritional_code == Food::HIGH && amount > 1) ? 2 : 1
end
...
end
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I notice a weird smell...
Could it be envy?
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Feature Envy
Move Method
Get rid of
with
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class Food
def calories(amount)
this_calories = 0
case nutritional_code
when HIGH
this_calories += (amount - 2) * 1.5 if amount > 2
this_calories += 5
when LOW
this_calories += amount * 3
when REGULAR
this_calories += (amount - 3) * 1.5 if amount > 3
this_calories += 1.5
end
end
def nutritional_points(amount)
(nutritional_code == HIGH && amount > 1) ? 2 : 1
end
end
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class Ingredient
def calories
food.calories(amount)
end
def nutritional_points
food.nutritional_points(amount)
end
end
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describe Ingredient do
let(:chorizo) { Food.new('chorizo', Food::HIGH) }
let(:lentil) { Food.new('lentil', Food::LOW) }
let(:potatoe) { Food.new('potatoe', Food::REGULAR) }
describe 'calories' do
it "with one regular food are 1.5"
it "with one regular food and amount > 3 are 3"
it "with one high food are 5"
it "with one high food and amount > 2 are 6.5"
it "with one low food are 3"
end
describe "nutritional points" do
it "is 2 if food is high and amount > 1"
it "is 1 if food is high and amount = 1"
it "is 1 if food is not high and amount = 1"
it "is 1 if food is not high and amount > 1"
end
end
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$ rspec spec/
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Finished in 0.00865 seconds
32 examples, 0 failures
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class Food
def calories(amount)
this_calories = 0
case nutritional_code
when HIGH
this_calories += (amount - 2) * 1.5 if amount > 2
this_calories += 5
when LOW
this_calories += amount * 3
when REGULAR
this_calories += (amount - 3) * 1.5 if amount > 3
this_calories += 1.5
end
end
def nutritional_points(amount)
(nutritional_code == HIGH && amount > 1) ? 2 : 1
end
end
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Replace Type Code with
State/Strategy
Switch Statements
Fix
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class Food
...
def nutritional_code=(value)
@nutritional_code = value
@nutritional_type = case @nutritional_code
when HIGH then HighNutritional.new
when LOW then LowNutritional.new
when REGULAR then RegularNutritional.new
end
end
def calories(amount)
@nutritional_type.calories(amount)
end
def nutritional_points(amount)
@nutritional_type.points(amount)
end
end
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module DefaultNutritionalPoints
def points(amount)
1
end
end
class RegularNutritional
include DefaultNutritionalPoints
def calories(amount)
acum = 1.5
acum += (amount - 3) * 1.5 if amount > 3
acum
end
end
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class LowNutritional
include DefaultNutritionalPoints
def calories(amount)
amount * 3
end
end
class HighNutritional
def calories(amount)
acum = 5
acum += (amount - 2) * 1.5 if amount > 2
acum
end
def points(amount)
amount > 1 ? 2 : 1
end
end
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EPIC
WIN!
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1. Introduction
2. Sample
3. Conclusions
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No Silver Bullet
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Improve Design
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Helps find bugs
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Program faster
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Good programmers write
code that humans can
understand
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Refactor
to Win
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¡Thanks!
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Questions?
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References
● Refactoring: Improving design of existing
code - Martin Fowler
● Refactoring to Patterns - Joshua Kerievsky
● Clean Code - Robert C. Martin
● Design Patterns in Ruby - Russ Olsen
● Source Making
http://sourcemaking.com/refactoring
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Tools
● Reek - Code Smell Detector for ruby
https://github.com/troessner/reek
● Rails Best Practices
http://rails-bestpractices.com
● Code Climate
http://codeclimate.com
● Ruby Refactoring Tool for Vim
https://github.com/ecomba/vim-ruby-refactoring
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Thanks!