The document discusses the SOLID principles of object-oriented design: - Single Responsibility Principle (SRP): A class should have one, and only one, reason to change. Symptoms include a class with multiple responsibilities or dependencies. - Open Closed Principle (OCP): A class should be open for extension but closed for modification. New functionality should not require changing existing code. - Liskov Substitution Principle (LSP): Derived classes must be substitutable for their base classes. - Interface Segregation Principle (ISP): Interfaces should be specific to the client and not contain methods that the client doesn't use. - Dependency Inversion Pr

1. SOLID | Štěpán Zikmund

3. krása

4. • změny v zadání
• nové funkce, které jsou v rozporu s
původní funkcionalitou
• deadliny
Co by mohly být takový překážky..

5. no, mohly by…

6. source code

7. 💩

8. Rigidity

9. Fragilitiy

10. Imobility

11. Coupling? How?

12. OOP

14. SOLID

15. Single Responsibility Principle
Open Closed Principle
Liskov Substitution Principle
Interface Segregation Principle
Dependency Inversion Principle

16. – Uncle Bob
„OOP is about managing dependency by
selectively inverted some key dependencies in
your architecture to prevent rigidity, fragility, not
reusability“

17. The Dependency
Inversion Principle
Depend on abstractions, not on concretions

18. m
n

19. m n

20. m interface
n

21. class Authentication
{
private $userProvider;
public function __construct(UserProvider $userProvider)
{
$this->userProvider = $userProvider;
}
}

22. class Authentication
{
private $userProvider;
public function __construct(UserProviderInterface $userProvider)
{
$this->userProvider = $userProvider;
}
}

23. The Single
Responsibility Principle
A class should have one, and only one, reason to
change

24. Symptomy
• účel třídy nejde pospat bez spojek a, nebo
• třída obsahuje velké množství properties a
public method
• třída obsahuje velké množství závislostí na další
objekty

25. Řešení
• kompozice
• event listener
• …

26. Employee
+ getSalary()
+ getName()
+ setSalary()
+ setName()
+ getSalaryReport()

27. Employee
+ getSalary()
+ getName()
+ setSalary()
+ setName()
SalaryReportBuilder
+ getReport(Employee $employee)

28. The Open Closed
Principle
You should be able to extend a classes behaviour,
without modifying it

29. Pro přidání nové featury
nechcete editovat stávající
kód, ale vytvořit nový

30. function doSomething($howToDoIt)
{
if ($howToDoIt == 'something') {
return someBehaviour();
} else if ($howToDoIt == 'somethingOther') {
return someOtherBehaviour();
} else {
throw new IllegalArgumentException();
}
}

31. Symptomy
• switch statement
• třída zná více různých service se stejným
interfacem nebo s podobným účelem

32. Employee
+ getSalary()
+ getName()
+ setSalary()
+ setName()
SalaryReportBuilder
+ getXmlReport(Employee $employee)
+ getJsonReport(Employee $employee)

33. Employee
+ getSalary()
+ getName()
+ setSalary()
+ setName()
SalaryReportBuilder
+ getXmlReport(Employee $employee)
+ getJsonReport(Employee $employee)
SRP

34. XmlReportBuilder
+ getXmlReport(..)
SalaryReportBuilder
+ getReport($type)
JsonReportBuilder
+ getJsonReport(..)

35. function getReport($type, $employee)
{
switch ($type):
case 'xml'
return $this->xmlReportBuilder->getReport($employee);
case 'json'
return $this->jsonReportBuilder->getReport($employee);
default:
throw new IllegalArgumentException();
}

36. function getReport($type, $employee)
{
switch ($type):
case 'xml'
return $this->xmlReportBuilder->getReport($employee);
case 'json'
return $this->jsonReportBuilder->getReport($employee);
default:
throw new IllegalArgumentException();
} OCP

37. XmlReportBuilder
+ getReport(..)
+ getName()
SalaryReportBuilder
+ addBuilder(ReportInterface)
+ getReport($type)
ReportBuilderInterface
+ getReport(..)
+ getName
JsonReportBuilder
+ getReport(..)
+ getName()

38. function getReport($type, $employee)
{
foraech ($this->reportBuilders as $builder) {
if ($builder->getName() == $type) {
return $builder->getReport($employee);
}
}
throw new IllegalArgumentException();
}

39. The Liskov
Substitution Principle
Derived classes must be substitutable for their base classes.

40. app rectangle

41. app rectangle
square

42. class Square
{
public function setHeight($height)
{
$this->height = $height;
parent::setWidth($height);
}
public function setWidth($width)
{
$this->width = $width;
parent::setHeight($width);
}
}

43. if ($rectangle instanceof Square) {
//..
} else {
//..
}

44. app rectangle
square

45. OOP není modelování
skutečného světa, ale
jeho reprezentací

46. class Rectangle
{
public function getHeight() {}
public function getWidth() {}
public function setHeight() {}
public function setWidth() {}
}
class Square
{
public function getSize() {}
public function setSize() {}
}

47. The Interface
Segregation Principle
Make fine grained interfaces that are client specific

48. m interface
n
Client specific?

49. m interface
n

50. Fine grained?
interface FileInterface
{
public function changeName()
public function changeOwner()
}

51. class DropboxFile implements FileInterface
{
public function changeName() { }
public function changeOwner()
{
// don’t need this method
}
}

52. interface FileInterface
{
public function changeName()
}
interface SupportsChangeOfOwnershipInterface
{
public function changeOwner()
}

53. SRP
OCP
LSP
ISP
DIP