SnapshotStateObserver

Helper class to efficiently observe snapshot state reads. See observeReads for more details.

NOTE: This class is not thread-safe, so implementations should not reuse observer between different threads to avoid race conditions.

Summary

Public constructors
SnapshotStateObserver(onChangedExecutor: (callback: () -> Unit) -> Unit)
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Public functions
Unit

Remove all observations.
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Unit
clear(scope: Any)

Clears all state read observations for a given scope.
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Unit
clearIf(predicate: (scope: Any) -> Boolean)

Remove observations using predicate to identify scopes to be removed.
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Unit
@TestOnly
notifyChanges(changes: Set<Any>, snapshot: Snapshot)

This method is only used for testing.
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Unit
<T : Any> observeReads(
    scope: T,
    onValueChangedForScope: (T) -> Unit,
    block: () -> Unit
)

Executes block, observing state object reads during its execution.
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Unit

Starts watching for state commits.
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Unit

Stops watching for state commits.
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Unit
withNoObservations(block: () -> Unit)

This function is deprecated. Replace with Snapshot.withoutReadObservation()
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Public constructors

SnapshotStateObserver

Cmn
Added in 1.0.0
SnapshotStateObserver(onChangedExecutor: (callback: () -> Unit) -> Unit)

Public functions

clear

Cmn
Added in 1.0.0
fun clear(): Unit

Remove all observations.

clear

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Added in 1.0.0
fun clear(scope: Any): Unit

Clears all state read observations for a given scope. This clears values for all onValueChangedForScope callbacks passed in observeReads.

clearIf

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Added in 1.0.0
fun clearIf(predicate: (scope: Any) -> Boolean): Unit

Remove observations using predicate to identify scopes to be removed. This is used when a scope is no longer in the hierarchy and should not receive any callbacks.

notifyChanges

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@TestOnly
fun notifyChanges(changes: Set<Any>, snapshot: Snapshot): Unit

This method is only used for testing. It notifies that changes have been made on snapshot.

observeReads

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Added in 1.0.0
fun <T : Any> observeReads(
    scope: T,
    onValueChangedForScope: (T) -> Unit,
    block: () -> Unit
): Unit

Executes block, observing state object reads during its execution.

The scope and onValueChangedForScope are associated with any values that are read so that when those values change, onValueChangedForScope will be called with the scope parameter.

Observation can be paused with Snapshot.withoutReadObservation.

Parameters
scope: T

value associated with the observed scope.
onValueChangedForScope: (T) -> Unit

is called with the scope when value read within block has been changed. For repeated observations, it is more performant to pass the same instance of the callback, as observedScopeMaps grows with each new callback instance.
block: () -> Unit

to observe reads within.

start

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Added in 1.0.0
fun start(): Unit

Starts watching for state commits.

stop

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Added in 1.0.0
fun stop(): Unit

Stops watching for state commits.

withNoObservations

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Added in 1.0.0
Deprecated in 1.2.0
fun withNoObservations(block: () -> Unit): Unit

Stops observing state object reads while executing block. State object reads may be restarted by calling observeReads inside block.