Module io.github.mmm.value.observable

Package io.github.mmm.value.observable

Interface ObservableEvent<V>

Type Parameters:

V - type of observed value.

public interface ObservableEvent<V>

Event notifying about changes of an ObservableValue.

Since:

1.0.0

See Also:

• ObservableEventListener
• ObservableValue

Method Summary

Modifier and Type	Method	Description
<M> M	getChange()
ObservableValue<V>	getObservable()
V	getOldValue()
V	getValue()
boolean	hasOldValue()
default boolean	isChange()

Method Details

getObservable

ObservableValue<V> getObservable()

Returns:

the ObservableValue that changed and send this event.

getValue

V getValue()

Returns:

the current value.

getOldValue

V getOldValue()

Returns:

the value before the change. May be null if the previous value was null or the old value is not available.

hasOldValue

boolean hasOldValue()

Returns:

true if the old value is available, false otherwise. For advanced performance the old value is not available for dynamically computed ObservableValues by default. It is guaranteed to be available if at least one of the registered ObservableEventListeners has called getValue() on the previous ObservableEvent forcing an eager evaluation.

getChange

<M> M getChange()

Type Parameters:

M - type of the change.

Returns:

the modification in case of a value change, null otherwise.

See Also:

• ListChange
• MapChange
• SetChange

isChange

default boolean isChange()

Returns:

true if the value object instance itself has changed. Most ObservableValues contain immutable value types (such as String, Boolean, Integer, BigDecimal, Instant, etc.). However, values like e.g. Collection are mutable and may support notifying changes. Otherwise, if false the observable itself was modified and its value has changed (or was invalidated and needs to be recalculated).

See Also:

• getChange()