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from typing import Callable, Optional, TypeVar
import reactivex
from reactivex import Observable, abc
from reactivex.disposable import CompositeDisposable, Disposable
_T = TypeVar("_T")
def using_(
resource_factory: Callable[[], abc.DisposableBase],
observable_factory: Callable[[abc.DisposableBase], Observable[_T]],
) -> Observable[_T]:
"""Constructs an observable sequence that depends on a resource
object, whose lifetime is tied to the resulting observable
sequence's lifetime.
Example:
>>> res = reactivex.using(lambda: AsyncSubject(), lambda: s: s)
Args:
resource_factory: Factory function to obtain a resource object.
observable_factory: Factory function to obtain an observable
sequence that depends on the obtained resource.
Returns:
An observable sequence whose lifetime controls the lifetime
of the dependent resource object.
"""
def subscribe(
observer: abc.ObserverBase[_T], scheduler: Optional[abc.SchedulerBase] = None
) -> abc.DisposableBase:
disp: abc.DisposableBase = Disposable()
try:
resource = resource_factory()
if resource is not None:
disp = resource
source = observable_factory(resource)
except Exception as exception: # pylint: disable=broad-except
d = reactivex.throw(exception).subscribe(observer, scheduler=scheduler)
return CompositeDisposable(d, disp)
return CompositeDisposable(
source.subscribe(observer, scheduler=scheduler), disp
)
return Observable(subscribe)
__all__ = ["using_"]
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