Refactoring When to Refactor? What to Refactor? Code Smells Catalogue of Refactorings

2. Cork Software Crafters

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4. Paulo Clavijo @pclavijo

5. Paulo Clavijo @pclavijo

6. Paulo Clavijo @pclavijo

7. Paulo Clavijo @pclavijo

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Paulo Clavijo @pclavijo

10. Paulo Clavijo @pclavijo

11. Paulo Clavijo @pclavijo

12. Paulo Clavijo @pclavijo

13. Paulo Clavijo @pclavijo

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Paulo Clavijo @pclavijo

15. Paulo Clavijo @pclavijo

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Paulo Clavijo @pclavijo

17. Paulo Clavijo @pclavijo

18. Paulo Clavijo @pclavijo

19. Paulo Clavijo @pclavijo

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Paulo Clavijo @pclavijo

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23. Paulo Clavijo @pclavijo

24. Paulo Clavijo @pclavijo
More of …
- Good names
- SOLID code
- Value objects
- Pure functions
...
Less of …
- Duplicate code
- Long Method
- Data Clumps
- Message Chains
...

25. Paulo Clavijo @pclavijo

26. Paulo Clavijo @pclavijo
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27. Paulo Clavijo @pclavijo
class Login {
private ContactInfo contactInfo;
public boolean authenticate(String userName, String password) {
// logic to validate that password:
// is at least 8 characters long
// contains a capital letter, a lowercase, a number …
…
// logic to verify if password matches user password
…
}

28. Paulo Clavijo @pclavijo
class User {
private ContactInfo contactInfo;
public User(ContactInfo contactInfo) {
this.contactInfo = contactInfo;
}
public String getFullAddress() {
String fullAddress = contactInfo.getStreetName() + " " +
contactInfo.getStreetNumber() + ", " +
contactInfo.getZipCode() + ", " +
contactInfo.getCity() + ", " +
contactInfo.getCountry();
return fullAddress;
}

29. Paulo Clavijo @pclavijo
class Invoice {
private Customer customer;
public Invoice(Customer customer) {
this.customer = customer;
}
public double getShippingCost() {
if (customer.getAddress().getCountry().isInEurope())
return STANDARD_SHIPPING_COST;
else
return OUTSIDE_EU_SHIPPING_COST;
}
...
}

30. Paulo Clavijo @pclavijo

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33. Paulo Clavijo @pclavijo

34. Paulo Clavijo @pclavijo

35. Paulo Clavijo @pclavijo

36. Paulo Clavijo @pclavijo

37. Paulo Clavijo @pclavijo
function getPayAmount() {
if (isDead) return deadAmount();
if (isSeparated) return separatedAmount();
if (isRetired) return retiredAmount();
return normalPayAmount();
}
function getPayAmount() {
let result;
if (isDead)
result = deadAmount();
else {
if (isSeparated)
result = separatedAmount();
else {
if (isRetired)
result = retiredAmount();
else
result = normalPayAmount();
}
}
return result;
}

38. Paulo Clavijo @pclavijo
if (summer())
charge = summerCharge();
else
charge = regularCharge();
if (!aDate.isBefore(plan.summerStart) && !aDate.isAfter(plan.summerEnd))
charge = quantity * plan.summerRate;
else
charge = quantity * plan.regularRate + plan.regularServiceCharge;

39. Paulo Clavijo @pclavijo
orders.filter(o => o.priority.higherThan(new Priority("normal")));
orders.filter(o => "high" === o.priority ||
"rush" === o.priority);

40. Paulo Clavijo @pclavijo
function amountInvoiced(aDateRange) {...}
function amountReceived(aDateRange) {...}
function amountOverdue(aDateRange) {...}
function amountInvoiced(startDate, endDate) {...}
function amountReceived(startDate, endDate) {...}
function amountOverdue(startDate, endDate) {...}

41. Paulo Clavijo @pclavijo
class Scorer {
constructor(candidate, medicalExam, scoringGuide) {
this._candidate = candidate;
this._medicalExam = medicalExam;
this._scoringGuide = scoringGuide;
}
execute() {
this._result = 0;
this._healthLevel = 0;
// long body code
}
}
function score(candidate, medicalExam, scoringGuide) {
let result = 0;
let healthLevel = 0;
// long body code
}

42. Paulo Clavijo @pclavijo
function setHeight(value) { this._height = value; }
function setWidth (value) { this._width = value; }
function setDimension(name, value) {
if (name === "height") {
this._height = value;
return;
}
if (name === "width") {
this._width = value;
return;
}
}

43. Paulo Clavijo @pclavijo
function totalOutstanding() {
return customer.invoices
.reduce((total, each) => each.amount + total, 0);
}
function sendBill() {
emailGateway.send(formatBill(customer));
}
function getTotalOutstandingAndSendBill() {
const result = customer.invoices
.reduce((total, each) => each.amount + total, 0);
sendBill();
return result;
}

44. Paulo Clavijo @pclavijo
const names = input
.filter(i => i.job === "programmer")
.map(i => i.name);
const names = [];
for (const i of input) {
if (i.job === "programmer")
names.push(i.name);
}

45. Paulo Clavijo @pclavijo
class EuropeanSwallow {
get plumage() { return 'average'; }
}
class AfricanSwallow {
get plumage() { return (this.numberOfCoconuts > 2) ? 'tired' : 'average'; }
}
class NorwegianBlueParrot {
get plumage() { return (this.voltage > 100) ? 'scorched' : 'beautiful'; }
}
switch (bird.type) {
case 'EuropeanSwallow':
return "average";
case 'AfricanSwallow':
return (bird.numberOfCoconuts > 2) ? "tired" : "average";
case 'NorwegianBlueParrot':
return (bird.voltage > 100) ? "scorched" : "beautiful";
default:
return "unknown";
}

46. Paulo Clavijo @pclavijo
function createEmployee(name, type) {
switch (type) {
case "engineer":
return new Engineer(name);
case "salesman":
return new Salesman(name);
case "manager":
return new Manager(name);
}
}
function createEmployee(name, type) {
return new Employee(name, type);
}

47. Paulo Clavijo @pclavijo
class UnknownCustomer {
get name() {return 'occupant';}
}
if (aCustomer === 'unknown') customerName = 'occupant';

48. Paulo Clavijo @pclavijo
const orderRecord = parseOrder(order);
const orderPrice = price(orderRecord, priceList);
function parseOrder(aString) {
const values = aString.split(/s+/);
return ({
productID: values[0].split("-")[1],
quantity: parseInt(values[1]),
});
}
function price(order, priceList) {
return order.quantity * priceList[order.productID];
}
const orderData = orderString.split(/s+/);
const productPrice = priceList[orderData[0].split("-")[1]];
const orderPrice = parseInt(orderData[1]) * productPrice;

49. Paulo Clavijo @pclavijo
leadEngineer = createEngineer(document.leadEngineer);
leadEngineer = new Employee(document.leadEngineer, 'E');

50. Paulo Clavijo @pclavijo

52. https://github.com/emilybache/Parrot-Refactoring-Kata

53. Paulo Clavijo @pclavijo
class EuropeanSwallow {
get plumage() { return 'average'; }
}
class AfricanSwallow {
get plumage() { return (this.numberOfCoconuts > 2) ? 'tired' : 'average'; }
}
class NorwegianBlueParrot {
get plumage() { return (this.voltage > 100) ? 'scorched' : 'beautiful'; }
}
switch (bird.type) {
case 'EuropeanSwallow':
return "average";
case 'AfricanSwallow':
return (bird.numberOfCoconuts > 2) ? "tired" : "average";
case 'NorwegianBlueParrot':
return (bird.voltage > 100) ? "scorched" : "beautiful";
default:
return "unknown";
}

54. Problem
Solution
You have a conditional that chooses different behaviors
depending on the type of an object.
Move each leg of the conditional to an overriding method
in a subclass. Make the original method abstract.

55. Mechanics
● If classes do not exist for polymorphic behavior, create them together
with a factory function to return the correct instance.
● Use the factory function in calling code.
● Move the conditional function to the superclass.
● If the conditional logic is not a self-contained function, use Extract
Function to make it so.
● Pick one of the subclasses. Create a subclass method that overrides the
conditional statement method. Copy the body of that leg of the
conditional statement into the subclass method and adjust it to fit.
● Repeat for each leg of the conditional.
● Leave a default case for the superclass method. Or, if superclass should
be abstract, declare that method as abstract or throw an error to show it
should be the responsibility of a subclass.

56. Paulo Clavijo @pclavijo

57. Paulo Clavijo @pclavijo

58. Paulo Clavijo @pclavijo

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Paulo Clavijo @pclavijo

62. Paulo Clavijo @pclavijo

63. Paulo Clavijo @pclavijo

64. https://refactoring.com/catalog
http://sourcemaking.com/refactoring/smells
Paulo Clavijo @pclavijo
Digital Rights Management