Binding a domain model with nullable fields in ItemViewModel - kotlin

Question

When running this code:
class PersonApp : App(PersonView::class)
class Person {
var name: String? = null
}
class PersonModel: ItemViewModel<Person>() {
val name = bind(Person::name)
}
class PersonView : View() {
val model: PersonModel by inject()
override val root = form {
textfield(model.name)
}
}
The following exception is thrown:
Nov 26, 2017 12:18:10 PM tornadofx.DefaultErrorHandler uncaughtException
SEVERE: Uncaught error
kotlin.TypeCastException: null cannot be cast to non-null type javafx.beans.property.Property<N>
at favetelinguis.bfgx.PersonModel$$special$$inlined$bindMutableNullableField$1.invoke(ViewModel.kt:538)
at favetelinguis.bfgx.PersonModel$$special$$inlined$bindMutableNullableField$1.invoke(ViewModel.kt:512)
at favetelinguis.bfgx.PersonModel.<init>(Exeee.kt:27)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at java.lang.Class.newInstance(Class.java:442)
at tornadofx.FXKt.find(FX.kt:413)
at favetelinguis.bfgx.Bree$$special$$inlined$inject$1.getValue(Component.kt:954)
at favetelinguis.bfgx.Bree$$special$$inlined$inject$1.getValue(Component.kt:151)
at favetelinguis.bfgx.Bree.getModel(Exeee.kt)
at favetelinguis.bfgx.Bree$root$1.invoke(Exeee.kt:20)
at favetelinguis.bfgx.Bree$root$1.invoke(Exeee.kt:17)
at tornadofx.FXKt.opcr(FX.kt:454)
at tornadofx.FormsKt.form(Forms.kt:23)
at favetelinguis.bfgx.Bree.<init>(Exeee.kt:19)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at java.lang.Class.newInstance(Class.java:442)
at tornadofx.FXKt.find(FX.kt:413)
at tornadofx.FXKt.find$default(FX.kt:398)
at tornadofx.App.start(App.kt:79)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
What is the idiomatic way of working with domain models where all the initial values are null and are to be set from the GUI? That is how can i change the code above to get it working as expected?

Answer 1

This should already be working in TornadoFX 1.7.13-SNAPSHOT, we did some improvements to nullable POJO's. An alternative approach (and better IMO) is to use JavaFX properties in your domain objects:
class Person {
val nameProperty = SimpleStringProperty()
var name by nameProperty
}
One last thing to consider is that you haven't set an initial item into your ViewModel. Remember that the ViewModel doesn't itself create instances of your item, you have to do that manually, or even give the ViewModel a default item when it's created:
class PersonModel : ItemViewModel<Person>(Person()) {
val name = bind(Person::name)
}