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O’zbek

Liskov Substitution Principle (LSP)

Quyi turlar (subtype’lar) asosiy turlar (base type’lar) o’rnida ishlatilganda dasturning to’g’ri ishlashiga ta’sir qilmasligi kerak.

Agar kod asosiy klass bilan ishlasa, uning istalgan subklassi bilan ham to’g’ri ishlashi shart — kutilmagan xatti-harakatlar bo’lmasligi kerak.

Diagramma

Noto’g’ri yondashuv

violation.py dagi Square klassi Rectangle‘dan meros oladi va setter’larni override qiladi — width va height doimo teng bo’lishi uchun. Bu Rectangle‘ning xatti-harakat shartnomasini buzadi:

class Square(Rectangle):
    def set_width(self, width: float) -> None:
        self._width = width
        self._height = width   # kutilmagan nojo'ya ta'sir!

    def set_height(self, height: float) -> None:
        self._width = height   # kutilmagan nojo'ya ta'sir!
        self._height = height

Width va height’ni mustaqil ravishda o’rnatadigan har qanday kod Square berilganda noto’g’ri natija beradi:

def resize_rectangle(rect: Rectangle, width: float, height: float) -> float:
    rect.set_width(width)
    rect.set_height(height)
    expected = width * height
    actual = rect.area()
    assert actual == expected  # Square uchun xatolik!

To’g’ri yondashuv

correct.py dagi Rectangle va Square ikkisi ham umumiy Shape abstraktsiyasidan meros oladi. Har bir shakl o’z geometriyasini mustaqil boshqaradi:

class Shape(ABC):
    @abstractmethod
    def area(self) -> float: ...

class Rectangle(Shape):
    def __init__(self, width: float, height: float) -> None:
        self.width = width
        self.height = height

    def area(self) -> float:
        return self.width * self.height

class Square(Shape):
    def __init__(self, side: float) -> None:
        self.side = side

    def area(self) -> float:
        return self.side ** 2

Ikkalasi ham Shape kutilgan joyda ishlatilishi mumkin — kutilmagan xatti-harakatlarsiz.