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Preventing direct creation

Метки: python

To disallow direct access to the classes, you can nest the classes within the factory method, like this:

# Factory/shapefact1/NestedShapeFactory.py
import random

class Shape(object):
    types = []

def factory(type):
    class Circle(Shape):
        def draw(self): print("Circle.draw")
        def erase(self): print("Circle.erase")

    class Square(Shape):
        def draw(self): print("Square.draw")
        def erase(self): print("Square.erase")

    if type == "Circle": return Circle()
    if type == "Square": return Square()
    assert 0, "Bad shape creation: " + type

def shapeNameGen(n):
    for i in range(n):
        yield factory(random.choice(["Circle", "Square"]))

# Circle() # Not defined

for shape in shapeNameGen(7):
    shape.draw()
    shape.erase()