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https://github.com/rjNemo/design-patterns
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69 lines
2.3 KiB
Python
69 lines
2.3 KiB
Python
from __future__ import annotations
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import copy
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from dataclasses import dataclass
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from typing import Any, List
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class SelfReferencingEntity:
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def __init__(self):
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self.parent = None
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def set_parent(self, parent):
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self.parent = parent
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@dataclass
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class SomeComponent:
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"""
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Python provides its own interface of Prototype via `copy.copy` and
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`copy.deepcopy` functions. And any class that wants to implement custom
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implementations have to override `__copy__` and `__deepcopy__` member
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functions.
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"""
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some_int: int
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some_list_of_objects: List
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some_circular_ref: Any
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def __copy__(self) -> SomeComponent:
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"""
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Create a shallow copy. This method will be called whenever someone
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calls `copy.copy` with this object and the returned value is returned
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as the new shallow copy.
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"""
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# First, let's create copies of the nested objects.
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some_list_of_objects = copy.copy(self.some_list_of_objects)
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some_circular_ref = copy.copy(self.some_circular_ref)
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# Then, let's clone the object itself, using the prepared clones of the
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# nested objects.
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new = self.__class__(self.some_int, some_list_of_objects, some_circular_ref)
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new.__dict__.update(self.__dict__)
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return new
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def __deepcopy__(self, memo={}) -> SomeComponent:
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"""
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Create a deep copy. This method will be called whenever someone calls
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`copy.deepcopy` with this object and the returned value is returned as
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the new deep copy.
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What is the use of the argument `memo`? Memo is the dictionary that is
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used by the `deepcopy` library to prevent infinite recursive copies in
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instances of circular references. Pass it to all the `deepcopy` calls
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you make in the `__deepcopy__` implementation to prevent infinite
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recursions.
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"""
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# First, let's create copies of the nested objects.
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some_list_of_objects = copy.deepcopy(self.some_list_of_objects, memo)
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some_circular_ref = copy.deepcopy(self.some_circular_ref, memo)
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# Then, let's clone the object itself, using the prepared clones of the
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# nested objects.
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new = self.__class__(self.some_int, some_list_of_objects, some_circular_ref)
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new.__dict__ = copy.deepcopy(self.__dict__, memo)
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return new
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