Support Immutable Model classes in ModelWrapper

[manuel-mauky]

Sometimes developers want to use immutable model classes. In this situation the ModelWrapper doesn't work because there is no classical "setter".

The ModelWrapper could provide a way to define fields by using an "Immutable setter" which is a function on an object that takes an argument for a field and returns a new instance of the object with this field changed:

public class ImmutablePerson {
    private final String name;

    public ImmutablePerson(String name) {
        this.name = name;
    }

    public ImmutablePerson withName(String newName) {
        return new ImmutablePerson(newName);
    }

    public String getName() {
        return name;
    }
}


ImmutablePerson hugo = new ImmutablePerson("Hugo");
ImmutablePerson hans = hugo.withName("Hans");

The ModelWrapper should provide methods like this:

ModelWrapper<ImmutablePerson> modelWrapper = new ModelWrapper<>();
StringProperty name = modelWrapper.fieldImmutable(ImmutablePerson::getName, ImmutablePerson::withName);

This way the user can change the name in the UI without actually changing the immutable person model that is behind the UI in the viewModel. Instead in the ViewModel one can get a new immutable person instance out of the ModelWrapper that has the new values from the UI.