SOLID Principles

Single Responsibility Principle

classDiagram
    class Book {
        +String title
        +String author
        +get_title() String
        +get_author() String
    }

    class BookRepository {
        +save(Book book) void
    }

    BookRepository ..> Book : uses

    note for Book "Manages book properties."
    note for BookRepository "Handles database interactions for the Book."

Open/Closed Principle

classDiagram
    class ShapeDrawer {
        +draw_shape(Shape shape) void
    }
    class Shape {
        +draw() void
    }
    class Circle {
        +draw() void
    }
    class Square {
        +draw() void
    }

    Shape <|-- Circle
    Shape <|-- Square
    ShapeDrawer o-- Shape

    note for Shape "New shapes can be added
by extending this class."
    note for ShapeDrawer "This class is closed for
modification but open
for extension."

Liskov Substitution Principle

classDiagram
    class Shape {
        +get_area() int
    }
    class Rectangle {
        -int width
        -int height
        +set_width(int width) void
        +set_height(int height) void
        +get_area() int
    }
    class Square {
        -int side
        +set_side(int side) void
        +get_area() int
    }

    Shape <|.. Rectangle
    Shape <|.. Square

    note "Both Rectangle and Square
can be used where a Shape
is expected."

Interface Segregation Principle

classDiagram
    class Workable {
        +work() void
    }
    class Feedable {
        +eat() void
    }
    class Human {
        +work() void
        +eat() void
    }
    class Robot {
        +work() void
    }

    Workable <|.. Human
    Feedable <|.. Human
    Workable <|.. Robot
    note "Classes now implement
only the interfaces relevant
to them."

Dependency Inversion Principle

classDiagram
    class Notification {
        -Notifier notifier
        +send_notification() void
    }
    class Notifier {
        +notify() void
    }
    class EmailNotifier {
        +notify() void
    }
    class SMSNotifier {
        +notify() void
    }

    Notifier <|.. EmailNotifier
    Notifier <|.. SMSNotifier
    Notification o-- Notifier

    note for Notification "Depends on the Notifier
abstraction, not a concrete
class."