Clean Code Cowboy

Have you ever had a fear of writing code? That maybe what you’re about to write makes no sense. Or maybe it’s not following best practices. Maybe it’s full of code smells? Or even worse maybe it doesn’t do what it’s supposed to do? You wrote something and you think “is this right and does it look OK!?”. Do you feel confident about your code? Are you happy with it? Programming is fun but it can be simply stressful - let’s just chill out, write a failing test and make it pass!

Transcript

1. Clean Code Cowboy
   by Piotr Solnica
   rubyconf.pt
   Portugal, Braga 2014
   

   View Slide

2. hi I’m Piotr Solnica aka solnic
   github.com/solnic
   solnic.eu
   @_solnic_
   

   View Slide

3. View Slide

4. clean coders
   

   View Slide

5. – Bob Martin from The Clean Coder book
   “Programmers who endure and
   succeed amidst swirling
   uncertainty and nonstop pressure
   share a common attribute: They
   care deeply about the practice of
   creating software. They treat it as
   a craft. They are professionals.”
   

   View Slide

6. cowboy coders
   

   View Slide

7. http://www.techrepublic.com/blog/10-things/10-types-
   of-programmers-youll-encounter-in-the-field/
   “The Code Cowboy is a force of
   nature that cannot be stopped. He
   or she is almost always a great
   programmer and can do work
   two or three times faster than
   anyone else. The problem is, at
   least half of that speed comes by
   cutting corners.”
   

   View Slide

8. Rules & Laws
   of
   Programming
   

   View Slide

9. Single Responsibility Principle
   Open/closed Principle
   Liskov Substitution Principle
   Interface Segregation Principle
   Dependency Inversion Principle
   

   View Slide

10. – DHH
    “I think Law of Demeter is shit”
    

    View Slide

11. – 300+ angry clean coders
    “IT’S THE LA
    W!!!1111”
    

    View Slide

12. who’s right?
    

    View Slide

13. – nobody, ever
    “I always wait for the green light”
    

    View Slide

14. “They’re more guidelines, than
    actual rules”
    

    View Slide

15. code smells
    

    View Slide

16. a code smell is a sign
    of a potential problem
    

    View Slide

17. following rules rigorously
    is a bad practice
    

    View Slide

18. the ease of refactoring
    is more important
    

    View Slide

19. Programming
    with
    Confidence
    

    View Slide

20. you know what you
    just wrote really works
    

    View Slide

21. you know what you just
    changed doesn’t break
    anything else
    

    View Slide

22. correctness verified by tests
    comes before concerns about
    implementation details
    

    View Slide

23. designing interfaces is
    more important than
    implementation details
    

    View Slide

24. confidence
    Great test coverage
    Continues Integration and Deployment
    Pair-programming
    Code review
    

    View Slide

25. Confidence
    ==
    Happiness
    

    View Slide

26. Testing in Ruby
    ==
    Awesome
    

    View Slide

27. My testing stack
    rspec
    bogus
    capybara
    vcr
    

    View Slide

28. describe Calculator do
    subject(:calculator) { Calculator.new }
    describe "#sum" do
    it "returns the sum of numbers" do
    expect(calculator.sum(2, 2)).to be(4)
    end
    end
    end
    

    View Slide

29. feature "Home page" do
    scenario "as a logged-in member I can buy add-ons", js: true, vcr: true do
    expect(page).to have_text("5 PT classes")
    click_on "Add"
    expect(page).to have_content("1,000,00 EUR")
    expect(page).to have_content("Buy")
    click_on "Buy"
    expect(page).to have_text("Thanks for buying an add-on")
    end
    end
    Use JavaScript
    driver
    Use VCR for
    stubbed remote
    calls
    

    View Slide

30. so simple!
    

    View Slide

31. so awesome!
    

    View Slide

32. Let’s write a failing
    test
    

    View Slide

33. Invoices App
    CRUD for customers
    CRUD for line items
    CRUD for invoices
    

    View Slide

34. feature "Customers" do
    scenario "As a user I can add a new customer and see it on the list" do
    visit new_customer_path
    find('#customer_name').set('Big Corp')
    find('#customer_email').set('accountant@bigcorp.test')
    find('#customer_address').set('Sunset Street 1')
    find('input[type=submit]').click
    expect(page).to have_text("Customer created")
    within(".customer-list") do
    expect(page).to have_text("Big Corp")
    end
    end
    end
    

    View Slide

35. class CustomersController < ApplicationController
    def index
    customers = Customer.all
    render locals: { customers: customers }
    end
    def new
    customer = Customer.new
    render locals: { customer: customer }
    end
    def create
    attributes = params.require(:customer).permit(:name, :email, :address)
    Customer.create(attributes)
    redirect_to :customers, notice: "Customer created"
    end
    end
    

    View Slide

36. Creating invoices
    

    View Slide

37. feature "Invoices" do
    let!(:customer) { Customer.create(name: "Big Corp") }
    scenario "As a user I can create a new invoice and see it on the list" do
    visit new_invoice_path
    find("#invoice_customer_id").select("Big Corp")
    find("#invoice_issue_date").set("2014-10-11")
    find("#invoice_delivery_date").set("2014-10-11")
    find("#invoice_due_date").set("2014-11-11")
    find("input[type=submit]").click
    expect(page).to have_text("Invoice created")
    within(".invoice-list") do
    expect(page).to have_text("DRAFT")
    expect(page).to have_text("Big Corp")
    expect(page).to have_text("2014-10-11")
    expect(page).to have_text("2014-11-11")
    end
    end
    end
    

    View Slide

38. class InvoicesController < ApplicationController
    def index
    invoices = Invoice.all
    render locals: { invoices: invoices }
    end
    def new
    invoice = Invoice.new
    customers = Customer.all
    render locals: { invoice: invoice, customers: customers }
    end
    def create
    attributes = params.require(:invoice).permit(
    :customer_id, :issue_date, :delivery_date, :due_date, :status
    )
    Invoice.create(attributes)
    redirect_to :invoices, notice: "Invoice created"
    end
    end
    

    View Slide

39. Turning point!
    

    View Slide

40. feature "Invoices" do
    scenario "As a user I can create a new invoice and see it on the list", js: true do
    visit new_invoice_path
    find("#invoice_customer_id").select("Big Corp")
    find("#invoice_issue_date").set("2014-10-11")
    find("#invoice_delivery_date").set("2014-10-11")
    find("#invoice_due_date").set("2014-11-11")
    find("#line-item-id").select("Development")
    find("#new-item-qty").set("2")
    find(“#add-new-item”).click
    within(".item-list") do
    expect(page).to have_text("Development")
    expect(page).to have_text("200.00")
    end
    find("input[type=submit]").click
    expect(page).to have_text("Invoice created")
    within(".invoice-list") do
    expect(page).to have_text("DRAFT")
    expect(page).to have_text("Big Corp")
    expect(page).to have_text("2014-10-11")
    expect(page).to have_text("2014-11-11")
    expect(page).to have_text("200.00")
    end
    end
    end
    Select line item and provide
    quantity
    Make sure the total amount is
    present
    Things will happen on the
    client-side so we need JS
    Make sure the item was added to
    the list
    

    View Slide

41. $form = $("#new_invoice")
    $itemSelect = $("#line-item-id")
    $lineItems = $("#line-items")
    $addButton = $("#add-new-item")
    $itemQty = $("#new-item-qty")
    $addButton.on('click', (e) ->
    e.preventDefault()
    quantity = $itemQty.val()
    item = $itemSelect.find(':selected').data()
    price = parseFloat(item.price) * parseFloat(quantity)
    $tr = $("").append(
    "#{item.name}#{item.unit}#{price}"
    )
    $form.append(
    $("").
    attr("type", "hidden").
    attr("name", "invoice[items][][line_item_id]").
    val(item.id)
    )
    $form.append(
    $("").
    attr("type", "hidden").
    attr("name", "invoice[items][][quantity]").
    val(quantity)
    )
    $lineItems.append($tr)
    )
    

    View Slide

42. View Slide

43. BUT!
    

    View Slide

44. View Slide

45. When it’s no longer simple to
    make a test pass it’s a good
    moment to write…more tests
    

    View Slide

46. Something must create an invoice along with its line
    items
    Something must be able to calculate the total amount
    based on line items
    

    View Slide

47. describe CreateInvoice do
    describe "#call" do
    it "creates an invoice with items" do
    customer = Customer.create(name: "Big Corp")
    magic = LineItem.create(name: 'Magic', unit: 'Hour', price: 2)
    healing = LineItem.create(name: 'Healing', unit: 'Hour', price: 4)
    today = Date.today
    params = {
    status: "DRAFT",
    customer_id: customer.id,
    issue_date: today,
    delivery_date: today,
    due_date: today + 1.month,
    items: [
    { line_item_id: magic.id, quantity: 2 },
    { line_item_id: healing.id, quantity: 3 },
    ]
    }
    create_invoice = CreateInvoice.new(params)
    invoice = create_invoice.call
    expect(invoice.customer).to eql(customer)
    expect(invoice.line_items.to_a).to eql([magic, healing])
    expect(invoice.total_amount).to eql(magic.price * 2 + healing.price * 3)
    end
    end
    end
    

    View Slide

48. class CreateInvoice
    attr_reader :params
    def initialize(params)
    @params = params
    end
    def call
    items = params[:items]
    invoice = Invoice.new(params.except(:items))
    items.each do |item|
    invoice.items.build(item)
    end
    invoice.save
    invoice
    end
    end
    

    View Slide

49. class Invoice < ActiveRecord::Base
    belongs_to :customer
    has_many :items, class_name: "InvoiceItem"
    has_many :line_items, through: :items
    def total_amount
    items.map { |item| item.line_item.price * item.quantity }.sum
    end
    end
    BUT WAIT A MINUTE!
    

    View Slide

50. LA
    W OF DEMETER VIOLATION!
    

    View Slide

51. OK moving on…
    

    View Slide

52. Let’s display an
    invoice
    

    View Slide

53. feature "Invoices" do
    fixtures(:all)
    let(:invoice) { invoices(:first) }
    let(:customer) { customers(:big_corp) }
    scenario "as a user I can display an invoice" do
    visit invoices_path
    click_on invoice.number
    expect(page).to have_content(customer.name)
    expect(page).to have_content(invoice.number)
    expect(page).to have_content(invoice.issue_date)
    expect(page).to have_content(invoice.delivery_date)
    expect(page).to have_content(invoice.due_date)
    expect(page).to have_content(invoice.total_amount)
    end
    end
    missing interface!
    

    View Slide

54. class Invoice < ActiveRecord::Base
    belongs_to :customer
    has_many :items, class_name: "InvoiceItem"
    has_many :line_items, through: :items
    # TODO: implement me
    alias_method :number, :id
    def total_amount
    items.map { |item| item.line_item.price * item.quantity }.sum
    end
    end
    there we go, all good
    

    View Slide

55. oh noez we must
    display line items too!
    

    View Slide

56. feature "Invoices" do
    fixtures(:all)
    let(:invoice) { invoices(:first) }
    let(:customer) { customers(:big_corp) }
    scenario "as a user I can display an invoice" do
    visit invoices_path
    click_on invoice.number
    expect(page).to have_content(customer.name)
    expect(page).to have_content(invoice.number)
    expect(page).to have_content(invoice.issue_date)
    expect(page).to have_content(invoice.delivery_date)
    expect(page).to have_content(invoice.due_date)
    expect(page).to have_content(invoice.total_amount)
    invoice.items.each do |item|
    expect(page).to have_content(item.line_item.name)
    expect(page).to have_content(item.line_item.price * item.quantity)
    end
    end
    end
    Demeter no likey :(
    

    View Slide

57. h1 = "#{invoice.id}"
    table
    thead
    tr
    th Customer
    th Issue date
    th Delivery date
    th Due date
    th Total amount
    tbody
    tr
    td = invoice.customer.name
    td = invoice.issue_date
    td = invoice.delivery_date
    td = invoice.due_date
    td = number_to_currency invoice.total_amount
    ul
    - invoice.items.each do |item|
    li = "#{item.line_item.name} #{number_to_currency(item.line_item.price *
    item.quantity)}"
    I told you mate but you
    wouldn’t listen!
    

    View Slide

58. OK let’s improve this
    

    View Slide

59. describe InvoiceItem do
    fixtures(:invoice_items, :line_items)
    subject(:invoice_item) { invoice_items(:one) }
    describe "#price" do
    let(:line_item) { line_items(:magic) }
    it "returns the price based on quantity and line-item price" do
    expect(invoice_item.price).to eql(line_item.price * invoice_item.quantity)
    end
    end
    end
    

    View Slide

60. class InvoiceItem < ActiveRecord::Base
    belongs_to :invoice
    belongs_to :line_item
    def price
    line_item.price * quantity
    end
    end
    class Invoice < ActiveRecord::Base
    # stuff
    def total_amount
    items.to_a.sum(&:price)
    end
    end
    

    View Slide

61. the story goes on…
    missing Invoice#number
    missing validations
    missing print-friendly invoice page
    …probably more, but it’s OK
    

    View Slide

62. Optimize for
    confidence and
    productiveness
    

    View Slide

63. Work on your testing
    skills!
    

    View Slide

64. Focus on correctness
    first
    

    View Slide

65. Learn how to write
    tests first
    

    View Slide

66. (even when writing a
    code spike!)
    

    View Slide

67. No rules or laws,
    just guidelines
    

    View Slide

68. Always be able to
    refactor with confidence
    

    View Slide

69. Don’t worry
    be happy
    

    View Slide

70. Thank you!
    <3<3<3
    

    View Slide

71. Questions? (:
    

    View Slide

72. Picture credits
    http://lol-rofl.com/cowboy-hat-front/
    http://thankheavens.com.au/2014/01/30/quick-fresh-
    gluten-free-ravioli-with-vine-ripe-tomato-and-toasted-
    garlic-sauce/
    http://www.zacksplaylist.com/bobby-mcferrin-dont-
    worry-be-happy-review/
    http://pl.wikipedia.org/wiki/Demeter
    

    View Slide