firestar5683
53 lines
1.4 KiB
Python
53 lines
1.4 KiB
Python
from typing import Callable, Optional, TypeVar
|
|
|
|
from reactivex import Observable, abc
|
|
|
|
_T = TypeVar("_T")
|
|
|
|
|
|
def default_if_empty_(
|
|
default_value: Optional[_T] = None,
|
|
) -> Callable[[Observable[_T]], Observable[Optional[_T]]]:
|
|
def default_if_empty(source: Observable[_T]) -> Observable[Optional[_T]]:
|
|
"""Returns the elements of the specified sequence or the
|
|
specified value in a singleton sequence if the sequence is
|
|
empty.
|
|
|
|
Examples:
|
|
>>> obs = default_if_empty(source)
|
|
|
|
Args:
|
|
source: Source observable.
|
|
|
|
Returns:
|
|
An observable sequence that contains the specified default
|
|
value if the source is empty otherwise, the elements of the
|
|
source.
|
|
"""
|
|
|
|
def subscribe(
|
|
observer: abc.ObserverBase[Optional[_T]],
|
|
scheduler: Optional[abc.SchedulerBase] = None,
|
|
) -> abc.DisposableBase:
|
|
found = [False]
|
|
|
|
def on_next(x: _T):
|
|
found[0] = True
|
|
observer.on_next(x)
|
|
|
|
def on_completed():
|
|
if not found[0]:
|
|
observer.on_next(default_value)
|
|
observer.on_completed()
|
|
|
|
return source.subscribe(
|
|
on_next, observer.on_error, on_completed, scheduler=scheduler
|
|
)
|
|
|
|
return Observable(subscribe)
|
|
|
|
return default_if_empty
|
|
|
|
|
|
__all__ = ["default_if_empty_"]
|