114 lines
3.4 KiB
Python
114 lines
3.4 KiB
Python
from __future__ import annotations
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from typing import TYPE_CHECKING, Callable, Optional, TypeVar
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from reactivex import abc
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from reactivex.internal.basic import default_error, noop
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from reactivex.typing import OnCompleted, OnError, OnNext
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_T_in = TypeVar("_T_in", contravariant=True)
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if TYPE_CHECKING:
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from reactivex.notification import Notification
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else:
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class Notification:
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pass
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class Observer(abc.ObserverBase[_T_in], abc.DisposableBase):
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"""Base class for implementations of the Observer class. This base
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class enforces the grammar of observers where OnError and
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OnCompleted are terminal messages.
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"""
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def __init__(
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self,
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on_next: Optional[OnNext[_T_in]] = None,
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on_error: Optional[OnError] = None,
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on_completed: Optional[OnCompleted] = None,
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) -> None:
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self.is_stopped = False
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self._handler_on_next: OnNext[_T_in] = on_next or noop
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self._handler_on_error: OnError = on_error or default_error
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self._handler_on_completed: OnCompleted = on_completed or noop
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def on_next(self, value: _T_in) -> None:
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"""Notify the observer of a new element in the sequence."""
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if not self.is_stopped:
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self._on_next_core(value)
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def _on_next_core(self, value: _T_in) -> None:
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"""For Subclassing purpose. This method is called by `on_next()`
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method until the observer is stopped.
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"""
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self._handler_on_next(value)
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def on_error(self, error: Exception) -> None:
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"""Notify the observer that an exception has occurred.
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Args:
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error: The error that occurred.
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"""
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if not self.is_stopped:
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self.is_stopped = True
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self._on_error_core(error)
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def _on_error_core(self, error: Exception) -> None:
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"""For Subclassing purpose. This method is called by `on_error()`
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method until the observer is stopped.
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"""
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self._handler_on_error(error)
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def on_completed(self) -> None:
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"""Notifies the observer of the end of the sequence."""
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if not self.is_stopped:
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self.is_stopped = True
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self._on_completed_core()
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def _on_completed_core(self) -> None:
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"""For Subclassing purpose. This method is called by `on_completed()`
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method until the observer is stopped.
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"""
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self._handler_on_completed()
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def dispose(self) -> None:
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"""Disposes the observer, causing it to transition to the
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stopped state."""
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self.is_stopped = True
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def fail(self, exn: Exception) -> bool:
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if not self.is_stopped:
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self.is_stopped = True
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self._on_error_core(exn)
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return True
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return False
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def throw(self, error: Exception) -> None:
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import traceback
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traceback.print_stack()
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raise error
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def to_notifier(self) -> Callable[[Notification[_T_in]], None]:
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"""Creates a notification callback from an observer.
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Returns the action that forwards its input notification to the
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underlying observer."""
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def func(notifier: Notification[_T_in]) -> None:
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return notifier.accept(self)
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return func
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def as_observer(self) -> abc.ObserverBase[_T_in]:
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"""Hides the identity of an observer.
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Returns an observer that hides the identity of the specified
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observer.
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"""
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return Observer(self.on_next, self.on_error, self.on_completed)
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