1. Object Calisthenics
Gabriel Heming

2. Gabriel Heming

3. ORIGEM Cal • is • then • ics - /ˌkaləsˈTHeniks/ Origem grega;
Exercícios no contexto de ginástica.

4. ORIGEM The ThoughtWorks Anthology - Jeff Bay; Conjunto de exercícios;
Nove regras (não universais);

5. MOTIVAÇÃO
Manutenibilidade;
Legibilidade;
Testabilidade;
Compreensão.

6. RESUMINDO

7. Only one level of indentation per method;
RULE #1:
Only one level of indentation per method;

8. 1 2 3 public String Board() { StringBuilder buf = new StringBuilder();
if (this.Data.Length >= 3)
for (int i = 0; i < this.Data.Length; i++)
for (int j = 0; j < this.Data[i].Length; j++)
buf.Append(this.Data[i][j]); }
buf.Append("\n");
return buf.ToString();
Validação 1 2 3 8

9. StringBuilder buf = new StringBuilder(); if (this.Data.Length < 3)
public String Board() {
StringBuilder buf = new StringBuilder();
if (this.Data.Length < 3)
return buf.ToString(); }
for (int i = 0; i < this.Data.Length; i++)
for (int j = 0; j < this.Data[i].Length; j++)
buf.Append(this.Data[i][j]);
buf.Append("\n");
Early return 9

10. EXTRACT METHOD
Martin Fowler

11. StringBuilder buf = new StringBuilder(); if (this.Data.Length < 3)
public String Board() {
StringBuilder buf = new StringBuilder();
if (this.Data.Length < 3)
return buf.ToString(); }
for (int i = 0; i < this.Data.Length; i++)
buf.Append(this.CollectColumns(this.Data[i]));
buf.Append("\n");
public String CollectColumns(string[] data)
foreach (string row in data)
buf.Append(row); 11

12. if (this.Data.Length < 3) return buf.ToString();
public String Board() {
if (this.Data.Length < 3) return buf.ToString();
return this.CollectRows(this.Data); }
public String CollectRows(string[][] data)
StringBuilder buf = new StringBuilder();
foreach (string[] row in data)
buf.Append(this.CollectColumns(row));
buf.Append("\n");
return buf.ToString();
public String CollectColumns(string[] data)
foreach (string row in data)
buf.Append(row); 12

13. Muito simples?

14. public static void SitefPaymentsAbort(Sales sales) {
foreach (Payment payment in sales.Payments)
if (payment.objSitefProvider != null && !string.IsNullOrEmpty(payment.objSitefProvider.receiptNumber))
payment.objSitefProvider.Abort(payment.objSitefProvider.receiptNumber, payment.objSitefProvider.DateTime); }
foreach (TenderLineItem tenderlineitem in ((RetailTransaction)sales.transaction).TenderLines)
if (tenderlineitem.LineId == payment.tenderLineItem.LineId)
if (tenderlineitem is GiftCertificateTenderLineItem)
if (sales.application.TransactionServices.CheckConnection())
bool released = true;
string comment = "";
sales.application.TransactionServices.GiftCardRelease(ref released, ref comment, ((GiftCertificateTenderLineItem)tenderlineitem).SerialNumber); 14

15. public static void SitefPaymentsAbort(Sales sales) {
foreach (Payment payment in sales.Payments)
SalesOrder.SitefPaymentAbort(sales , payment); }
private static void SitefPaymentAbort(Sales sales, Payment payment)
if (payment.objSitefProvider != null && !string.IsNullOrEmpty(payment.objSitefProvider.receiptNumber))
payment.objSitefProvider.Abort(payment.objSitefProvider.receiptNumber, payment.objSitefProvider.DateTime);
foreach (TenderLineItem tenderlineitem in ((RetailTransaction)sales.transaction).TenderLines)
if (tenderlineitem.LineId == payment.tenderLineItem.LineId)
if (tenderlineitem is GiftCertificateTenderLineItem)
if (sales.application.TransactionServices.CheckConnection())
bool released = true;
string comment = "";
sales.application.TransactionServices.GiftCardRelease(ref released, ref comment, ((GiftCertificateTenderLineItem)tenderlineitem).SerialNumber); 15

16. private static void SitefPaymentAbort(Sales sales, Payment payment) {
/** código omitido **/
foreach (TenderLineItem tenderlineitem in ((RetailTransaction)sales.transaction).TenderLines)
if (tenderlineitem.LineId == payment.tenderLineItem.LineId)
if (tenderlineitem is GiftCertificateTenderLineItem)
if (sales.application.TransactionServices.CheckConnection())
bool released = true;
string comment = "";
sales.application.TransactionServices.GiftCardRelease(ref released, ref comment, ((GiftCertificateTenderLineItem)tenderlineitem).SerialNumber); }
Validações 16

17. private static void SitefPaymentAbort(Sales sales, Payment payment) {
/** código omitido **/
IEnumerable<TenderLineItem> tenderLineItemList = ((RetailTransaction)sales.transaction).TenderLines.Where(
tenderLineItem =>
tenderLineItem.LineId == payment.tenderLineItem.LineId
&& tenderLineItem is GiftCertificateTenderLineItem );
foreach (TenderLineItem tenderlineitem in tenderLineItemList)
if (sales.application.TransactionServices.CheckConnection())
bool released = true;
string comment = "";
sales.application.TransactionServices.GiftCardRelease(ref released, ref comment, ((GiftCertificateTenderLineItem)tenderlineitem).SerialNumber); } 17

18. private static void SitefPaymentAbort(Sales sales, Payment payment) {
/** código omitido **/
IEnumerable<TenderLineItem> tenderLineItemList = ((RetailTransaction)sales.transaction).TenderLines.Where(
tenderLineItem =>
tenderLineItem.LineId == payment.tenderLineItem.LineId
&& tenderLineItem is GiftCertificateTenderLineItem );
foreach (TenderLineItem tenderlineitem in tenderLineItemList)
SalesOrder.GiftCardRelease(sales, tenderLineItem); }
private static void GiftCardRelease(SalesOrder sales, TenderLineItem tenderlineitem)
if (sales.application.TransactionServices.CheckConnection())
bool released = true;
string comment = "";
sales.application.TransactionServices.GiftCardRelease(ref released, ref comment, ((GiftCertificateTenderLineItem)tenderlineitem).SerialNumber); 18

19. public static void SitefPaymentsAbort(Sales sales){
foreach (Payment payment in sales.Payments)
SalesOrder.SitefPaymentAbort(sales , payment); }
private static void SitefPaymentAbort(Sales sales, Payment payment)
if (payment.objSitefProvider != null && !string.IsNullOrEmpty(payment.objSitefProvider.receiptNumber))
payment.objSitefProvider.Abort(payment.objSitefProvider.receiptNumber, payment.objSitefProvider.DataHoraTransacao);
IEnumerable<TenderLineItem> tenderLineItemList = ((RetailTransaction)sales.transaction).TenderLines.Where(
tenderLineItem =>
tenderLineItem.LineId == payment.tenderLineItem.LineId
&& tenderLineItem is GiftCertificateTenderLineItem );
foreach (TenderLineItem tenderlineitem in tenderLineItemList)
SalesOrder.GiftCardRelease(sales, tenderLineItem);
private static void GiftCardRelease(SalesOrder sales, TenderLineItem tenderlineitem)
if (sales.application.TransactionServices.CheckConnection())
bool released = true;
string comment = "";
sales.application.TransactionServices.GiftCardRelease(ref released, ref comment, ((GiftCertificateTenderLineItem)tenderlineitem).SerialNumber); 19

20. BENEFÍCIOS S.R.P. (Single Responsibility Principle);
Redução lógica por métodos;
Legibilidade;
Reusabilidade.

21. RULE #2:
Don’t use the
else keyword

22. Por que?

23. COMPLEXIDADE CICLOMÁTICA

24. Defensive Programming

25. public Entity Create(Entity entity) { if (entity.IsValid())
Repository repository = this.GetRepository(entity);
if (!repository.Exists(entity))
return repository.Save(entity); }
else
throw new ArgumentException("The entity already exists");
throw new ArgumentException("Invalid entity"); 25

26. public Entity Create(Entity entity) { if (!entity.IsValid())
throw new ArgumentException("Invalid entity"); }
Repository repository = this.GetRepository(entity);
if (!repository.Exists(entity))
return repository.Save(entity);
else
throw new ArgumentException("The entity already exists"); 26

27. public Entity Create(Entity entity) { if (!entity.IsValid())
throw new ArgumentException("Invalid entity"); }
Repository repository = this.GetRepository(entity);
if (repository.Exists(entity))
throw new ArgumentException("The entity already exists");
return repository.Save(entity); 27

28. OUTRAS ABORDAGENS
Chain of Responsibility Pattern;
State Pattern.

29. BENEFÍCIOS Evita duplicidade; Aumenta a legibilidade;
Reduz a complexidade ciclomática.

30. RULE #3:
Wrap all primitives 
and STRINGS

31.  Primitive Obsession 
anti-pattern

32. SOMENTE TIPOS
COM COMPORTAMENTO

33. 87,43 Sub 0?? 77,43 ????????? Add -10?? class BankAccount{
private double amount;
public void Add(double money)
this.amount += money; }
public void Sub(double money)
this.amount -= money;
public double Total()
return this.amount;
BankAccount account = new BankAccount();
account->Add(10);
account->Add(12.25);
account->Add(27.50);
account->Add(55);
account->Sub(17.32);
account->Total();
87,43
account->Add(-10);
account->Sub(0);
account->Total();
Sub 0??
77,43 ?????????
Add -10?? 33

34. Lógica duplicada class BankAccount { private double amount;
public void Add(double money)
if (money <= 0)
throw new ArgumentException("money não pode ser igual ou menor que zero"); }
this.amount += money;
public void Sub(double money)
this.amount -= money;
public double Total()
return this.amount;
Lógica duplicada 34

35. private double amount; public Money(double amount) if (money <= 0)
class Money {
private double amount;
public Money(double amount)
if (money <= 0)
throw new ArgumentException("money não pode ser igual ou menor que zero"); }
this.amount = amount;
public double GetAmount()
return this.amount;
class BankAccount {
private double amount;
public void Add(Money money)
this.amount += money->GetAmount(); }
public void Sub(Money money)
this.amount -= money->GetAmount();
public double Total()
return this.amount;
BankAccount account = new BanckAccount();
account->Add(new Money(10)); 
account->Add(new Money(-10)); // throw ArgumentException 35

36. BENEFÍCIOS
Evita duplicidade;
Encapsulamento;
Domain Driven Design.

37. First class collections
RULE #4:
First class collections

38. public List<Address> AddressList { get; internal set; } }
public class Person {
public List<Address> AddressList { get; internal set; } }
public class Address
public Type Type { get ; set; }
public enum Type
Residential,
Commercial
List<Address> residentialAddressList = person.AddressList.Where(
address => address.Type == Type.Residential
).ToList()
List<Address> residentialAddressList = person.AddressList.Where(
address => address.Type == Type.Commercial
).ToList() 38

39. E SE PRECISAR FILTRAR EM DIFERENTES LUGARES?

40. Responsabilidades demais
class Person {
public List<Address> AddressList { get; internal set; }
public List<Address> GetResidentialAddressList()
return this.AddressList.Where(
address => address.Type == Type.Residential).ToList(); }
public List<Address> GetCommercialAddressList()
address => address.Type == Type.Commercial).ToList();
Responsabilidades demais
List<Address> residentialAddressList = person.GetResidentialAddressList();
List<Address> commercialAddressList = person.GetCommercialAddressList(); 40

41. CADA UM COM SUA RESPONSABILIDADE

42. public class AddressCollection {
public List<Address> GetResidentialAddressList()
return this.AddressList.Where(
address => address.Type == Type.Residential).ToList(); }
public List<Address> GetCommercialAddressList()
address => address.Type == Type.Commercial).ToList();
public class Person
public AddressCollection AddressCollection { get; internal set; }
List<Address> residentialAddressList = person.AddressCollection.GetResidentialAddressList();
List<Address> commercialAddressList = person.AddressCollection.GetCommercialAddressList(); 42

43. BENEFÍCIOS S.R.P. (Single Responsibility Principle); Evita duplicação;
Manutenibilidade.

44. RULE #5:
One dot per line

45. TRAIN WRECKS
Robert UncleBob Martin

46. this.Repository.Database.Config.SetAttribute("attribute" , "value");
E se houver um null? 46

47. Null object?

48. POR QUE NÃO? Esconde um problema de encapsulamento;
Difícil de debugar e tratar exceções;
O código deve ser reestruturado e tomar consciência da existência dele;
Prejudica a leitura e o entendimento.

49. LAW OF DEMETER

50. this.Repository.SetDatabaseConfig("attribute", "value");
Nem sempre é aplicável 50

51. EXCEÇÕES Fluent Interface;
Builders (ex.: Query Builder, Link Builder, etc...);

52. BENEFÍCIOS Lei de Demeter; O.C.P (Open/Closed Principle);
Legibilidade;
Testabilidade;
Debug.

53. RULE #6:
Don’t abbreviate

54. POR QUE ABREVIAR? Escrita repetitiva? Nomes muito longos?
“There are 2 hard problems in computer science: cache invalidation, naming things, and off-by-1 errors.”

55. BENEFÍCIOS S.R.P. (Single Responsibility Principle); Comunicação;
Legibilidade;
Manutenibilidade.

56. Keep all entities small
RULE #7:
Keep all entities small

57. DIRETRIZES Classes com 50 linhas; Leitura com pouco uso de scroll;
Apenas desenvolva o que for utilizar.

58. BENEFÍCIOS S.R.P. (Single Responsibility Principle); Legibilidade;
Encapsulamento;
Segregação;
Coesão e Coerência.

59. No classes with more than two instance variables
RULE #8:
No classes with more than two instance variables

60. ESSA É DIFÍCIL

61. List<String> names;
class Name {
String first;
String middle;
String last; }
class Name {
Surname family;
GivenNames given; }
class Surname
String family;
class GivenNames
List<String> names; 61

62. Por que somente duas?

63. COMPLEMENTAR A REGRA #2

64. BENEFÍCIOS S.R.P. (Single Responsability Principle);
Baixo acoplamento;
Encapsulamento;
Coesão e Coerência;
Testabilidade.

65. No getters / setters / properties
RULE #9:
No getters / setters / properties

66. POR QUE?
Simplesmente uma questão comportamental.

67. public int X { get; set; } public int Y { get; set; } }
class Rectangle {
public int X { get; set; }
public int Y { get; set; } }
Rectangle rectangle = new Rectangle() {
X = 10,
Y = 5 };
int area = rectangle.X * rectangle.Y; 67

68. TELL, DON’T ASK!

69. public Rectangle(int x , int y) this.X = x; this.Y = y; }
class Rectangle {
private int X;
private int Y;
public Rectangle(int x , int y)
this.X = x;
this.Y = y; }
public int TotalArea()
return this.X * this.Y;
Rectangle rectangle = new Rectangle(10, 5);
int area = rectangle.TotalArea(); 69

70. BENEFÍCIOS
O.C.P (Open/Closed Principle);
Encapsulamento.

71. CONSIDERAÇÕES

72. QUESTIONS?
Thanks!