86 lines
2.5 KiB
Python
86 lines
2.5 KiB
Python
from typing import Optional, TypeVar, cast
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from .. import abc
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from ..disposable import Disposable
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from .innersubscription import InnerSubscription
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from .subject import Subject
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_T = TypeVar("_T")
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class AsyncSubject(Subject[_T]):
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"""Represents the result of an asynchronous operation. The last value
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before the close notification, or the error received through
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on_error, is sent to all subscribed observers."""
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def __init__(self) -> None:
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"""Creates a subject that can only receive one value and that value is
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cached for all future observations."""
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super().__init__()
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self.value: _T = cast(_T, None)
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self.has_value: bool = False
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def _subscribe_core(
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self,
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observer: abc.ObserverBase[_T],
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scheduler: Optional[abc.SchedulerBase] = None,
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) -> abc.DisposableBase:
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with self.lock:
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self.check_disposed()
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if not self.is_stopped:
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self.observers.append(observer)
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return InnerSubscription(self, observer)
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ex = self.exception
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has_value = self.has_value
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value = self.value
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if ex:
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observer.on_error(ex)
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elif has_value:
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observer.on_next(value)
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observer.on_completed()
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else:
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observer.on_completed()
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return Disposable()
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def _on_next_core(self, value: _T) -> None:
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"""Remember the value. Upon completion, the most recently received value
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will be passed on to all subscribed observers.
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Args:
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value: The value to remember until completion
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"""
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with self.lock:
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self.value = value
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self.has_value = True
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def _on_completed_core(self) -> None:
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"""Notifies all subscribed observers of the end of the sequence. The
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most recently received value, if any, will now be passed on to all
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subscribed observers."""
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with self.lock:
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observers = self.observers.copy()
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self.observers.clear()
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value = self.value
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has_value = self.has_value
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if has_value:
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for observer in observers:
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observer.on_next(value)
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observer.on_completed()
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else:
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for observer in observers:
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observer.on_completed()
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def dispose(self) -> None:
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"""Unsubscribe all observers and release resources."""
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with self.lock:
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self.value = cast(_T, None)
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super().dispose()
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