IndirectObservableValue

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