glok-model/uk.co.nickthecoder.glok.property/DefaultIndirectObservableValue

DefaultIndirectObservableValue

open class DefaultIndirectObservableValue<P : Any, V>(val parentProperty: ObservableValue<P?>, val defaultValue: V, val getObservable: (P) -> ObservableValue<V>) : LazyObservableValue<V>

Tracks a value of a property where we don't have the property itself, but only another property, (parentProperty) from which we can access the required property.

Imagine we have a class Person, with : val nameProperty : StringProperty

Now suppose we have :

val personProperty : Property

Note that personProperty.value can be null.

The following will give us an ObservableValue which changes whenever personProperty changes, and also changes whenever that person's name changes.

val personNameProperty : ObservableValue = IndirectObservableValue( personProperty, "" ) {
    person -> person.nameProperty.value
}

When personProperty.value == null, then personNameProperty.value == "<None>", not null.

Alas, personNameProperty is not of type ObservableString. To work around the JVM's limited type system, consider creating a boilerplate class :

class IndirectObservableString(
    parentProperty: ObservableValue,
    defaultValue: String,
    getObservable: (P) -> ObservableValue
) : IndirectObservableValue(parentProperty, defaultValue, getObservable), ObservableString

Inheritors

DefaultIndirectObservableBoolean

DefaultIndirectObservableOptionalBoolean

DefaultIndirectObservableByte

DefaultIndirectObservableOptionalByte

DefaultIndirectObservableChar

DefaultIndirectObservableOptionalChar

DefaultIndirectObservableDouble

DefaultIndirectObservableOptionalDouble

DefaultIndirectObservableFloat

DefaultIndirectObservableOptionalFloat

DefaultIndirectObservableInt

DefaultIndirectObservableOptionalInt

DefaultIndirectObservableLong

DefaultIndirectObservableOptionalLong

DefaultIndirectObservableString

DefaultIndirectObservableOptionalString

DefaultIndirectObservableFile

DefaultIndirectObservableOptionalFile

Constructors

DefaultIndirectObservableValue

constructor(parentProperty: ObservableValue<P?>, defaultValue: V, getObservable: (P) -> ObservableValue<V>)

Properties

defaultValue

val defaultValue: V

The default value to use when parentProperty.value == null.

getObservable

val getObservable: (P) -> ObservableValue<V>

A lambda to get the ObservableValue we are interested in tracking, from the value of parentProperty.

parentProperty

val parentProperty: ObservableValue<P?>

value

open override val value: V

Functions

addBindChangeListener

open override fun addBindChangeListener(listener: ChangeListener<V, ObservableValue<V>>)

Identical to addChangeListener, but these listeners are guaranteed to fire BEFORE other listeners. These should be used for the sole purpose of updating single ObservableValues which are dependent on this ObservableValue. This helps (but doesn't guarantee) that properties change atomically. i.e. when one property changes, a related property also changes before other (regular) listeners fire. Therefore, the (regular) listeners cannot read inconsistent values.

open fun addBindChangeListener(lambda: (ObservableValue<V>, V, V) -> Unit): ChangeListener<V, ObservableValue<V>>

addBindListener

open fun addBindListener(lambda: (Observable) -> Unit): InvalidationListener

open override fun addBindListener(listener: InvalidationListener)

Identical to addListener, but these listeners are guaranteed to fire BEFORE regular listeners. These should be used for the sole purpose of updating other ObservableValues which are dependent on this Observable.