44 lines
1.4 KiB
Python
44 lines
1.4 KiB
Python
from asyncio import Future
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from typing import Callable, Optional, TypeVar, Union
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from reactivex import Observable, abc, from_future, throw
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from reactivex.scheduler import ImmediateScheduler
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_T = TypeVar("_T")
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def defer_(
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factory: Callable[[abc.SchedulerBase], Union[Observable[_T], "Future[_T]"]]
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) -> Observable[_T]:
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"""Returns an observable sequence that invokes the specified factory
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function whenever a new observer subscribes.
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Example:
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>>> res = defer(lambda scheduler: of(1, 2, 3))
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Args:
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observable_factory: Observable factory function to invoke for
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each observer that subscribes to the resulting sequence. The
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factory takes a single argument, the scheduler used.
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Returns:
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An observable sequence whose observers trigger an invocation
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of the given observable factory function.
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"""
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def subscribe(
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observer: abc.ObserverBase[_T], scheduler: Optional[abc.SchedulerBase] = None
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) -> abc.DisposableBase:
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try:
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result = factory(scheduler or ImmediateScheduler.singleton())
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except Exception as ex: # By design. pylint: disable=W0703
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return throw(ex).subscribe(observer)
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result = from_future(result) if isinstance(result, Future) else result
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return result.subscribe(observer, scheduler=scheduler)
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return Observable(subscribe)
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__all__ = ["defer_"]
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