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import pytest |
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from software_patterns import Observer, Subject |
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def test_observers_sanity_test(): |
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subject1: Subject = Subject([]) |
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subject2: Subject = Subject([]) |
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assert hasattr(subject1, '_observers') |
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assert hasattr(subject2, '_observers') |
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assert id(subject1._observers) != id(subject2._observers) |
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# def test_observer_as_constructor(observer: t.Type[Observer]): |
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def test_observer_as_constructor(): |
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import sys |
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observer = Observer |
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with pytest.raises(TypeError) as instantiation_from_interface_error: |
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_observer_instance = observer() # type: ignore[abstract] |
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error_msg = str(instantiation_from_interface_error.value) |
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if sys.version_info >= (3, 12): |
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expected = "Can't instantiate abstract class Observer without an implementation for abstract method 'update'" |
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assert error_msg == expected |
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else: |
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import re |
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runtime_exception_message_reg = r"Can't instantiate abstract class Observer with abstract methods? update" |
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assert re.match(runtime_exception_message_reg, error_msg) |
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# def test_scenario(subject: t.Type[Subject], observer: t.Type[Observer]): |
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def test_scenario(): |
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# Scenario 1 |
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# The client code. |
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class ObserverA(Observer): |
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def update(self, *args, **kwargs) -> None: |
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print("ObserverA: Reacted to the event") |
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s1: Subject = Subject([]) |
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o1 = ObserverA() |
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s1.attach(o1) |
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# business logic |
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s1.state = 0 |
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s1.notify() |
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# Scenario 2 |
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class Businessubject(Subject): |
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def some_business_logic(self) -> None: |
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""" |
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Usually, the subscription logic is only a fraction of what a Subject can |
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really do. Subjects commonly hold some important business logic, that |
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triggers a notification method whenever something important is about to |
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happen (or after it). |
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""" |
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print("\nSubject: I'm doing something important.") |
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self._state = 2 |
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print(f"Subject: My state has just changed to: {self._state}") |
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self.notify() |
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class ObserverB(Observer): |
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def update(self, *args, **kwargs) -> None: |
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subject = args[0] |
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if subject.state == 0 or subject.state >= 2: |
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print("ObserverB: Reacted to the event") |
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s2 = Businessubject([]) |
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assert id(s1) != id(s2) |
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assert id(s1._observers) != id(s2._observers) |
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o1, o2 = ObserverA(), ObserverB() |
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s2.add(o1, o2) |
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# business logic |
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print(s2._observers) |
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s2.some_business_logic() |
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s2.some_business_logic() |
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s2.detach(o1) |
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s2.some_business_logic() |
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boromir674 /
software-patterns
