DSL or NoDSL - Euruko - 29may2010

DSL or NoDSL?

José Valim blog.plataformatec.com @josevalim

DSL or NoDSL?

ID blog twitter


A brief introduction...


A short story...


mail_form


Contact form recipe


Contact form recipe

✦ Controller (20 LOC)


Contact form recipe

✦ Model (30 LOC)


Contact form recipe

✦ Model (30 LOC)

✦ View (30 LOC)


Contact form recipe

✦ Model (30 LOC)

✦ View (30 LOC)

✦ Mailer (15 LOC)


Contact form recipe

✦ Model (30 LOC)

✦ View (30 LOC)

✦ Mailer (15 LOC)
✦ View (20 LOC)


Let’s create a DSL!


Domain Speci c Language


class ContactForm < MailForm::Base
to "jose.valim@plataformatec.com.br"
from "contact_form@app_name.com"
subject "Contact form"

attributes :name, :email, :message
end

ContactForm.new(params[:contact_form]).deliver


from { |c| "#{c.name} <#{c.email}>" }


to :author_email

def author_email
Author.find(self.author_id).email
end


headers { |c|
{ "X-Spam" => "True" } if c.honey_pot
}


to :author_email
from { |c| "#{c.name} <#{c.email}>" }
subject "Contact form"

headers { |c|
{ "X-Spam" => "True" } if c.honey_pot
}


def author_email
end
end


Issues


Issues

✦ Lacks simplicity


Issues

✦ Lacks simplicity
✦ Reduces programmer happiness


NoDSL!


From: GitHub <noreply@github.com>
To: jose.valim@plataformatec.com.br
Message-Id: <4bfe3e812c22fc17d@github.com>
Subject: [GitHub] someone commented on a commit
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8

MESSAGE BODY



def headers
{
:to => author_email,
:from => "#{name} <#{email}>",
:subject => "Contact form"
}
end

def author_email
end
end


It provides a nice DSL


It relies on a simple contract


Rack


class RackApp
def self.call(env)
[200, { "Content-Type" => "text/html"}, ["Hello"]]
end
end


RackApp = Rack::AppBuilder.new do |env|
status 200
headers "Content-Type" => "text/html"
body ["Hello"]

after_return {
# do something
}
end


Rake and Thor


task :process do
# do some processing
end

namespace :app do
task :setup do
# do some setup
#
end
end

rake app:setup


task :process do
end

namespace :app do
task :setup do
# do some setup
Rake::Task[:process].invoke
end
end

rake app:setup


class Default < Thor
def process
end
end

class App < Thor
def setup
# do some setup
#
end
end

thor app:setup


class Default < Thor
def process
end
end

class App < Thor
def setup
# do some setup
Default.new.process
end
end

thor app:setup


Rspec and Test::Unit


# Rspec
describe User do
it "should be valid" do
User.new(@attributes).should be_valid
end
end

# Test::Unit
class UserTest < Test::Unit::Case
def test_user_validity
assert User.new(@attributes).valid?
end
end


A nal story...


class UsersController < ApplicationController
def index
@users = User.all

respond_to do |format|
format.html # index.html.erb
format.xml { render :xml => @users }
end
end

def show
@user = User.find(params[:id])

format.html # show.html.erb
format.xml { render :xml => @user }
end
end

def new
@user = User.new

format.html # new.html.erb
format.xml { render :xml => @user }
end
end

def edit
end

Scaﬀold Controller
def create
@user = User.new(params[:user])

if @user.save
format.html { redirect_to(@user, :notice => 'User was successfully created.') }
format.xml { render :xml => @user, :status => :created, :location => @user }
else
format.html { render :action => "new" }
format.xml { render :xml => @user.errors, :status => :unprocessable_entity }
end
end
end

def update

if @user.update_attributes(params[:user])
format.html { redirect_to(@user, :notice => 'User was successfully updated.') }
format.xml { head :ok }
else
format.html { render :action => "edit" }
format.xml { render :xml => @user.errors, :status => :unprocessable_entity }
end
end
end

def destroy
@user.destroy

format.html { redirect_to(users_url) }
format.xml { head :ok }
end
end
end


restful!
end


restful!

create do
before {
# do something before
}

success.flash "This is the message"
end

create.after do
# do something after
end
end


InheritedResources


class UsersController < InheritedResources::Base
def create
# do something before
flash[:success] = "This is the message"
super
# do something after
end
end


Bene ts


Bene ts

✦ Simple


Bene ts

✦ Simple
✦ Less code to maintain


Bene ts

✦ Simple

✦ More time to focus on important

features


Bene ts

✦ Simple

✦ More time to focus on important

features
✦ Just Ruby™


ORM Callbacks


# DSL
class User < ActiveRecord::Base
after_save :deliver_notification, :unless => :admin?
end

# NoDSL
class User < ActiveRecord::Base
def save(*)
if super
deliver_notification unless admin?
end
end
end


Thank you!


Questions? Feedback?
Opinions?


Questions? Feedback?
Opinions?

ID blog twitter


DSL or NoDSL - Euruko - 29may2010

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