/**
 * Generates a writable property that represents the selected value for this toggele group.
 * If the toggles are configured with a value (@see #togglebutton and #radiogroup) the corresponding
 * toggle will be selected when this value is changed. Likewise, if the toggle is changed by clicking
 * it, the value for the toggle will be written to this property.
  * To bind to this property, use the #ToggleGroup.bind() function.
 */
fun <T> ToggleGroup.selectedValueProperty(): ObjectProperty<T> =
        properties.getOrPut("tornadofx.selectedValueProperty") {
            SimpleObjectProperty<T>().apply {
                selectedToggleProperty().onChange {
                    value = it?.properties?.get("tornadofx.toggleGroupValue") as T?
                }
                onChange { selectedValue ->
                    selectToggle(toggles.find { it.properties["tornadofx.toggleGroupValue"] == selectedValue })
                }
            }
        } as ObjectProperty<T>