Writing Your Own Ruby DSL

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Nossa Senhora de Perpétuo Socorro

Linguagem de programação focada em um domínio/tarefa especíﬁco

Remove código desnecessário ao realizar uma tarefa

driver = Selenium::WebDriver.for :chrome driver.navigate.to "google.com" input = driver.find_element(:name, 'q')

input.send_keys('ruby') button = driver.find_element(:name, 'lst-ib') button.click #capybara visit 'google.com' fill_in 'Search', with: 'ruby' click_button 'Google Search'

driver = Selenium::WebDriver.for :chrome driver.navigate.to "google.com" input = driver.find_element(:name, 'q')

input.send_keys('ruby') button = driver.find_element(:name, 'lst-ib') button.click #capybara visit 'google.com' fill_in 'Search', with: 'ruby' click_button 'Google Search'

HTML <html> <head> <title></title> </head> <body> </body> </html>

CSS html, body { width: 100%; height: 100%; overflow: hidden;

}

Gherkin (Cucumber) Feature: Serve coffee Coffee should not be served

until paid for Coffee should not be served until the button has been pressed If there is no coffee left then money should be refunded Scenario: Buy last coffee Given there are 1 coffees left in the machine And I have deposited 1$ When I press the coffee button Then I should be served a coffee

Internal

RSpec # these two expectations... expect(alphabet).to start_with("a") expect(alphabet).to end_with("z") #

...can be combined into one expression: expect(alphabet).to start_with("a").and end_with( "z")

Factory Girl FactoryGirl.define do factory :user do first_name "John" last_name

"Doe" admin false end factory :admin, class: User do first_name "Admin" last_name "User" admin true end end

yield struct instance_eval self procs send lambda class method_missing blocks

Pizza Cookbook DSL

Quit the bullshit, let’s code!

new_pizza 'Frango Catupiry' do add_vegetable 'tomatoes' add_sauce 'barbecue' add_cheese 'catupiry'

add_topping 'chicken' end

new_pizza('Frango Catupiry’) do add_vegetable(‘tomatoes') add_sauce('barbecue') add_cheese('catupiry') add_topping(‘chicken') end

block yield struct

block [1, 2, 3].each do |n| puts n end #=>

1 #=> 2 #=> 3

yield def execute_this_code yield end execute_this_code { puts 'Hey guys!'

} #=> Hey guys!

class User attr_accessor :name, :age def initialize name, age @name

= name @age = age end end User = Struct.new(:name, :age) struct

new_pizza 'Frango Catupiry' do add_vegetable 'tomatoes' add_sauce 'barbecue' add_cheese 'catupiry'

add_topping 'chicken' end

Pizza = Struct.new(:name, :vegetable, :cheese, :sauce, :topping) def add_vegetable name

@pizza.vegetable = name end #def add_sauce, add_cheese... def create_pizza name @pizza = Pizza.new(name) yield if block_given? end new_pizza 'Frango Catupiry' do add_vegetable 'tomatoes' add_sauce 'barbecue' add_cheese 'catupiry' add_topping 'chicken' end

Pizza = Struct.new(:name, :vegetable, :cheese, :sauce, :topping) def add_vegetable name

2 grandes problemas

poluindo o namespace global

só um topping?

Cookbook.new_pizza "X-Tudo" do add_vegetable 'tomatoes' add_sauce 'barbecue' add_cheese 'cheddar' add_toppings

'chicken', 'peperoni', 'bacon' end

Cookbook.new_pizza "X-Tudo" do add_vegetable 'tomatoes' add_sauce 'barbecue' add_cheese 'cheddar' add_toppings

multiple arguments

multiple arguments def my_method *args puts args end my_method 1,

2, '3' #=> [1, 2, '3']

Proc/lambda times_two = Proc.new do |n| n * 2 end

times_two = lambda do |n| n * 2 end times_two.call(2) #=> 4

ampersand square = Proc.new do |n| n ** 2 end

[1, 2].each(square) #won't work [1, 2].each(&square)#will convert #the proc to a block

ampersand square = Proc.new do |n| n ** 2 end

[1, 2].each(square) #won't work [1, 2].each(&square)#will convert #the proc to a block

class Alphabet def self.each_letter(&block) #converts block into proc ('A'..'Z').each(&block) #converts

proc into block end end Alphabet.each_letter { |l| puts l } ampersand

class Alphabet def self.each_letter(&block) #converts block into proc ('A'..'Z').each(&block) #converts

proc into block end end Alphabet.each_letter { |l| puts l } #=> 'A' #=> 'B' #=> 'C' ampersand

instance_eval

instance_eval class User attr_accessor :name end user = User.new user.name

#=> nil user.instance_eval do @name = 'My new name' end user.name #=> 'My new name'

instance_eval class User attr_accessor :name end user = User.new user.name

Cookbook.new_pizza "X-Tudo" do add_vegetable 'tomatoes' add_sauce 'barbecue' add_cheese 'cheddar' add_toppings

#pizza.rb class Pizza attr_accessor :name, :vegetable, :cheese, :sauce, :toppings def

initialize name @name = name end def add_vegetable name @vegetable = name end def add_sauce name @sauce = name end def add_cheese name @cheese = name end def add_toppings *args raise "Too many toppings man!" if args.size > 4 @toppings = args end end

#pizza.rb class Pizza attr_accessor :name, :vegetable, :cheese, :sauce, :toppings def

initialize name @name = name end def add_vegetable name @vegetable = name end def add_sauce name @sauce = name end def add_cheese name @cheese = name end def add_toppings *args raise "Too many toppings man!" if args.size > 4 @toppings = args end end

#pizza.rb class Pizza #... def add_toppings *args raise "Too many

toppings man!" if args.size > 4 @toppings = args end end

#cookbook.rb class Cookbook @pizzas = [] def self.new_pizza name, &block

pizza = Pizza.new(name) pizza.instance_eval(&block) if block_given? @pizzas << pizza end def self.pizzas @pizzas end end

#cookbook.rb class Cookbook @pizzas = [] def self.new_pizza name, &block

Cookbook.new_pizza "X-Tudo" do add_vegetable 'tomatoes' add_sauce 'barbecue' add_cheese 'cheddar' add_toppings

DRY?

#pizza.rb class Pizza # ... def add_vegetable name @vegetable =

name end def add_sauce name @sauce = name end def add_cheese name @cheese = name end # ... end

#pizza.rb class Pizza # ... def add_vegetable name @vegetable =

self send method_missing

None

self

class User attr_accessor :name def forget_my_name! self.name = nil end

end user = User.new user.name = 'Joao' user.name #=> 'Joao' user.forget_my_name! user.name #=> nil

class User attr_accessor :name def forget_my_name! self.name = nil end

None

self

None

send

user = User.new user.name = 'Joao' user.name #=> "Joao" user.send

'name' #=> "Joao" user.send 'name=', 'Pedro' user.name #=> Pedro

user = User.new user.name = 'Joao' user.name #=> "Joao" user.send

method_missing

class Comment def method_missing(method_name, *args) puts "Voce tentou chamar o

metodo #{method_name} com os argumentos #{args}" end end comment = Comment.new comment.nao_existe_blabla 1, 3, '5' #=>Voce tentou chamar o metodo nao_existe_blabla com os argumentos [1,3,'5']

class Comment def method_missing(method_name, *args) puts "Voce tentou chamar o

#pizza.rb class Pizza # ... def add_vegetable name @vegetable =

class Pizza #... private def method_missing method_sym, *args method_name =

method_sym.to_s if method_name.start_with? "add_" attribute_name = method_name.split(/^add_/)[1] self.send(attribute_name + "=", args[0]) else super end end end

class Pizza #... private def method_missing method_sym, *args method_name =

method_sym.to_s if method_name.start_with? "add_" attribute_name = method_name.split(/^add_/)[1] self.send(attribute_name + "=", args[0]) #pizza.cheese= 'cheddar' else super end end end

#pizza.rb class Pizza # ... def add_vegetable name @vegetable =

class Pizza ... private def method_missing method_sym, *args method_name =

Cookbook.new_pizza "X-Tudo" do add_vegetable 'tomatoes' add_sauce 'barbecue' add_cheese 'cheddar' add_toppings

RSpec it "should start with 'a'" do expect(alphabet).to start_with("a") end

Cookbook.new_pizza "Frango Catupiry" do add_vegetable 'tomatoes' add_sauce 'barbecue' add_cheese 'catupiry'

add_toppings 'chicken', 'bacon' bake_for(15.minutes).on(:high_temperature) end

#bake_time.rb class BakeTime attr_accessor :duration, :temperature def initialize duration @duration

= duration end def on temperature @temperature = temperature end end

#bake_time.rb class BakeTime attr_accessor :duration, :temperature def initialize duration @duration

class Pizza attr_accessor :bake_time, #:cheese... def bake_for duration @bake_time =

BakeTime.new(duration) end #... end

class Pizza attr_accessor :bake_time, #:cheese... def bake_for duration @bake_time =

BakeTime.new(duration) end #... end

Writing Your Own Ruby DSL - Tropical Ruby 2015

Writing Your Own Ruby DSL - Tropical Ruby 2015

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