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MI L'ANIMA 

WHY DO WE LOVE RUBY? 

EASY TO READ 

COMMUNITY ▸ 100k+ gem on rubygems.org ▸ 3rd repo language on GitHub1 1 according to GitHub Language Trends 

RUBY ISN'T COOL ANYMORE AND WE ARE FINE WITH THAT. 

TESTING CULTURE 

RUBY ON RAILS 

ALL THAT GLITTERS IS NOT GOLD 

RUBY IS SLOW BUT RUBY 2.0 HAS MADE GOOD PROGRESS 2 2 Garbage collection in ruby 2.0 

NOT SUITED FOR PARALLELISM 3 3 MRI have GIL lock, JRuby doesn't. More about GIL. 

CODING TIME 

DSL DOMAIN-SPECIFIC LANGUAGE 

DSL [...] a computer language that's targeted to a particular kind of problem, rather than a general purpose language that's aimed at any kind of software problem.4 — Martin Fowler 4 Martin Fowler article 

class Recipe attr_accessor :name, :ingredients, :difficulty # defines getters and setters def initialize @ingredients = [] end def add_ingredient(ingredient) ingredients << ingredient end def cook! puts "Cooking #{name} (#{difficulty})," puts "with: #{ingredients.join(", ")}." puts "Buon appetito!" end end 

recipe = Recipe.new recipe.name = "spaghetti con polpette" recipe.difficulty = :easy recipe.add_ingredient("spaghetti") recipe.add_ingredient("polpa di pomodoro") recipe.add_ingredient("polpette") recipe.cook! "Cooking spaghetti con polpette (easy), with: spaghetti, polpa di pomodoro, polpette. Buon appetito!" 

module RecipeBook @collection = {} def self.add(recipe) @collection[recipe.name] = recipe end def self.get(name) @collection[name] end end 

recipe = Recipe.new recipe.name = "spaghetti con polpette" [...] RecipeBook.add(recipe) RecipeBook.get("spaghetti con polpette").cook! "Cooking [...]" 

WE WANT THIS RecipeBook.add do name "Spaghetti con polpette" difficulty :easy ingredient "spaghetti" ingredient "passata di pomodoro" ingredient "polpette" end 

ATTEMPT #1 

module RecipeBook [...] def self.add(&block) recipe = Recipe.new recipe.instance_eval(&block) @collection[recipe.name] = recipe end [...] end 

RecipeBook.add do self.name = "spaghetti con polpette" self.difficulty = :easy add_ingredient("spaghetti") add_ingredient("passata di pomodoro") add_ingredient("polpette") end 

UGLY ! 

WE WANT THIS! RecipeBook.add do name "Spaghetti con polpette" difficulty :easy ingredient "spaghetti" ingredient "passata di pomodoro" ingredient "polpette" end 

ATTEMPT #2 

class RecipeBuilder attr_reader :recipe def initialize @recipe = Recipe.new end def name(name) recipe.name = name end def difficulty(difficulty) recipe.difficulty = difficulty end def ingredient(ingredient) recipe.add_ingredient(ingredient) end end 

module RecipeBook @collection = {} def self.add(&block) builder = RecipeBuilder.new builder.instance_eval(&block) recipe = builder.recipe @collection[recipe.name] = recipe end def self.get(name) @collection[name] end end 

RecipeBook.add do name("spaghetti con polpette") difficulty(:easy) ingredient("spaghetti") ingredient("passata di pomodoro") ingredient("polpette") end 

RecipeBook.add do name "spaghetti con polpette" difficulty :easy ingredient "spaghetti" ingredient "passata di pomodoro" ingredient "polpette" end 

! 

REFACTORING 

class RecipeBuilder attr_reader :recipe def initialize @recipe = Recipe.new end def name(name) recipe.name = name end def difficulty(difficulty) recipe.difficulty = difficulty end def ingredient(ingredient) recipe.add_ingredient(ingredient) end end 

class RecipeBuilder attr_reader :recipe DELEGATED_SETTERS = [:name, :difficulty] def initialize @recipe = Recipe.new end def method_missing(method_name, *args) if DELEGATED_SETTERS.include?(method_name) recipe.send("#{method_name}=", *args) # e.g.: name=("spaghetti con polpette") else super end end def ingredient(ingredient) recipe.add_ingredient(ingredient) end end 

BOOKS ▸ Practical Object-Oriented Design in Ruby ▸ Metaprogramming Ruby 2 

QUESTIONS TIME 

VI È VENUTA FAME? SOURCE CODE: HTTP://BIT.LY/1NWGAJT @delphaber @welaika