I wondered if someone can shed some light on this question, when to use
Single.fromCallable( ()-> myObject )
instead of
Single.just(myObject)
from the documentation, Single.fromCallable()
:
/**
* Returns a {@link Single} that invokes passed function and emits its result for each new SingleObserver that subscribes.
* <p>
* Allows you to defer execution of passed function until SingleObserver subscribes to the {@link Single}.
* It makes passed function "lazy".
* Result of the function invocation will be emitted by the {@link Single}.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code fromCallable} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param callable
* function which execution should be deferred, it will be invoked when SingleObserver will subscribe to the {@link Single}.
* @param <T>
* the type of the item emitted by the {@link Single}.
* @return a {@link Single} whose {@link SingleObserver}s' subscriptions trigger an invocation of the given function.
*/
and the documentation for Single.just()
:
/**
* Returns a {@code Single} that emits a specified item.
* <p>
* <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.just.png" alt="">
* <p>
* To convert any object into a {@code Single} that emits that object, pass that object into the
* {@code just} method.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code just} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param item
* the item to emit
* @param <T>
* the type of that item
* @return a {@code Single} that emits {@code item}
* @see <a href="http://reactivex.io/documentation/operators/just.html">ReactiveX operators documentation: Just</a>
*/