Package io.objectbox.reactive

Class SubscriptionBuilder<T>

java.lang.Object

io.objectbox.reactive.SubscriptionBuilder<T>

Type Parameters:

T - The data type the DataObserver subscribes to.

public class SubscriptionBuilder<T>
extends java.lang.Object

Builds a DataSubscription for a DataObserver passed via observer(DataObserver). Note that the call to observer(DataObserver) is mandatory to create the subscription - if you forget it, nothing will happen.

When subscribing to a data source such as Query, this builder allows to configure:

• weakly referenced observer via weak()
• a data transform operation via transform(DataTransformer)
• error handlers via onError(ErrorObserver)
• calling the observer using a custom Scheduler (e.g. Android main thread) via on(Scheduler)

Note: the order of methods called in this do not matter. Unlike Rx's Observeable, this builder just collects all info. For example, on(scheduler).transform(transformer) is the same as transform(transformer).on(scheduler).

Constructor Summary

Constructors

Constructor	Description
SubscriptionBuilder(DataPublisher<T> publisher, java.lang.Object param)

Method Summary

Modifier and Type	Method	Description
SubscriptionBuilder<T>	dataSubscriptionList(DataSubscriptionList dataSubscriptionList)
DataSubscription	observer(DataObserver<T> observer)	Sets the observer for this subscription and requests the latest data to be delivered immediately.
SubscriptionBuilder<T>	on(Scheduler scheduler)	Changes the thread in which the DataObserver (and potentially @ErrorObserver) is called.
SubscriptionBuilder<T>	onError(ErrorObserver errorObserver)	The given ErrorObserver is notified when the DataTransformer (transform(DataTransformer)) or DataObserver (observer(DataObserver)) threw an exception.
SubscriptionBuilder<T>	onlyChanges()	Upon subscribing do not deliver the latest data, only once there are changes.
SubscriptionBuilder<T>	single()	Only deliver the latest data once, do not subscribe for data changes.
<TO> SubscriptionBuilder<TO>	transform(DataTransformer<T,TO> transformer)	Transforms the original data from the publisher to some other type.
SubscriptionBuilder<T>	weak()	Uses a weak reference for the observer.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SubscriptionBuilder

@Internal
public SubscriptionBuilder(DataPublisher<T> publisher,
                           @Nullable
                           java.lang.Object param)

Method Detail

weak

public SubscriptionBuilder<T> weak()

Uses a weak reference for the observer. It is still advised to remove observers explicitly if possible: relying on the garbage collection may cause non-deterministic timing. Until the weak reference is actually cleared by GC, it may still receive notifications.

single

public SubscriptionBuilder<T> single()

Only deliver the latest data once, do not subscribe for data changes.

See Also:

onlyChanges()

onlyChanges

public SubscriptionBuilder<T> onlyChanges()

Upon subscribing do not deliver the latest data, only once there are changes.

See Also:

single()

transform

public <TO> SubscriptionBuilder<TO> transform(DataTransformer<T,TO> transformer)

Transforms the original data from the publisher to some other type. All transformations run sequentially in an asynchronous thread owned by the publisher.

This is similar to the map operator of Rx and Kotlin.

Type Parameters:

TO - The type data is transformed to.

onError

public SubscriptionBuilder<T> onError(ErrorObserver errorObserver)

The given ErrorObserver is notified when the DataTransformer (transform(DataTransformer)) or DataObserver (observer(DataObserver)) threw an exception.

on

public SubscriptionBuilder<T> on(Scheduler scheduler)

Changes the thread in which the DataObserver (and potentially @ErrorObserver) is called.

In the Android package, there is a class AndroidScheduler with a MAIN_THREAD Scheduler implementation. Using MAIN_THREAD, observers will be called in Android's main thread, which is required for UI updates.

observer

public DataSubscription observer(DataObserver<T> observer)

Sets the observer for this subscription and requests the latest data to be delivered immediately. Subscribes to receive data updates. This can be changed by using single() or onlyChanges().

Results are delivered on a background thread owned by the internal data publisher, unless a scheduler was set using on(Scheduler).

The returned DataSubscription must be canceled once the observer should no longer receive data.

dataSubscriptionList

public SubscriptionBuilder<T> dataSubscriptionList(DataSubscriptionList dataSubscriptionList)