Hi all,
I am writing a field component for a simple immutable value object which
is essentially the following:
public class IntegerRange {
private int minimum, maximum;
public IntegerRange(int minimum, int maximum) {
if (minimum > maximum)
throw new IllegalArgumentException();
this.minimum = minimum;
this.maximum = maximum;
}
public int getMaximum() { return maximum; }
public int getMinimum() { return minimum; }
}
Now this value object is being used as part of a domain object so in the
form, I have:
private class BulkEditForm extends Form {
public BulkEditForm(String id) {
super(id, new CompoundPropertyModel(new Template()));
add(new IntegerRangeField("seats"));
}
}
I am using the TextField component for minimum and maximum fields so the
HTML of my IntegerRangeField panel looks like this:
<?xml version="1.0" encoding="utf-8"?>
<wicket:panel>
<input wicket:id="min" type="text" class="text numeric" size="8" />
-
<input wicket:id="max" type="text" class="text numeric" size="8" />
</wicket:panel>
However, I don't know how to write a proper model for IntegerRangeField
component. I obviously cannot just do new Model(new IntegerRange(...))
because user input needs to be validated first and the immutable value
object doesn't allow invalid state. So, I probably need to store both,
minimum and maximum, in separate models for the two input fields. But
then I don't know how to update the 'seats' property in class Template!
I have tried overriding setObject() method for the two models for
updating the IntegerRange model, but then I need to add bunch of state
validation to ensure I don't feed invalid arguments to IntegerRange
constructor. Furthermore, I already have the validation in a
IFormValidator implementation so duplicating it doesn't seem to make too
much sense.
So how do I write a model for an immutable value object with state
validation?
Thanks,
Pekka
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